The most common identifiable mode of spread is through iatrogenic invasive
procedures; intravenous drug users are the largest group of carriers.
Sexual transmission is a significant risk. Vertical transmission
(from infected mother to child) is possible. Most HBV infections
are asymptomatic, especially in childhood, but manifest themselves as disease
in a third of infected adults. It commences with malaise, lethargy,
anorexia, nausea, vomiting, and upper abdominal pain. A minority
of patients develop a mild fever, rash, acute rheumatoid arthritis.
Two days to two weeks following this prodromal stage, the icteric phase
ensues, involving dark urine, pale stools, and jaundice. Convalescence
may require several weeks. 1% of icteric cases end in fatality.
Some develop chronic hepatitis becoming asymptomatic carriers or in some
cases developing cirrhosis and possibly hepatocellular cancer.
Vaccine Preparation
The vaccine was originally formulated by purifying antigen from the
blood of chronically infected carriers. Hepatis B surface antigen
(HBsAg) particles were purified from the sera, followed by chemical treatment
to inactivate any accompanying HBV or other virus. In the U.S., this
procedure has been replaced with Recombivax (Merck) and Engerix-B (SmithKline
Biologicals) vaccines produced by recombinant DNA technology. The
recombinant vaccines are formulated by using HBsAG synthesized by cultivating
common bakers' yeast (Saccharomyces cerevisiae) into which a plasmid
containing the gene for HBsAg has been inserted. The yeast cells
are lysed and HBsAg is purified by biochemical techniques. The protein
subunit is adsorbed to aluminum hydroxide. The vaccines are packaged
to contain 10-49 ug of HBsAg/ml, and thimerosal is added as a preservative.
They must be maintained at temperatures between 2o C and 8o
C;
they must not be frozen.
Dosage
The vaccine schedule for adults and children uses three intramuscular
injections; in the deltoid of adults and children, in the thigh of infants.
The vaccinations should be made at 0, 1, and 6 months; various time schedules
have been established. Using the Recombivax vaccine, infants of both
HBsAg+ mothers and HBsAg- mothers require 5 ug/0.5 ml, adults 10 ug/1.0
ml, and immunocompromised patients 40 ug/1.0 ml. The Energix-B vaccine
requires that infants receive a dosage of 10 ug/0.5 ml, children and adults
10 ug/1.0 ml, and immunocompromised persons 40 ug/2.0 ml. Clinical
tests have shown that they are 80%-95% effective in preventing HBV infection
and clinical hepatitis among susceptible children and adults. The
vaccines provide a continued high level of protection from chronic HBV
infections for at least five years.
Side Effects and
Precautions
The vaccine is safe to administer to adults and children. The
most frequently reported side effects include pain at the injection site
(3-29%) and a temperature greater than 37.7o C
(1-6%). Allergic reations are very low (1 event per 600,000 vaccine
doses distributed). A possible association may link the neurological
disorder, Guillain-Barre syndrome, with receipt of the first dose of plasm-derived
hepatitis B vaccine (5/1,000,000 vaccinees). Patients allergic to
yeast or any of the preservative components must not receive the vaccine.
Who Needs It?
The vaccine is recommended for newborn babies of HBsAg positive mothers,
immigrants from countries with a high HBV prevalence, close contacts of
HBV carriers, intravenous drug users, homosexually active men, heterosexually
promiscuous individuals, hemophiliacs and others requiring frequent transfusions,
health care workers exposed to human blood, and travelers to HBV endemic
areas.
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Human influenza viruses are characterized by their immunogenic surface
receptors hemagluttinin (HA: subtypes H1, H2, and H3), and neuraminidase
(NA: subtypes N1 and N2). Infection with a virus of one subtype
confers little immunity to an infection with another subtype. Antigenic
variation within the same strain is responsible for the yearly occurrence
of flu epidemics. Influenza is typified by rapid onset, high fever,
respiratory symptoms, nonproductive cough, and muscular aches and pains
lasting for several days. Serious complications are prevalent in
elderly individuals and those with underlying health problems. High-risk
groups may develop influenza pneumonia or secondary bacterial pneumonia
leading to possible mortality. 25-150 per 100,000 people over the
age of 65 die each season.
Preparation
Basing its judgment on global surveillance, the World Health Organization
makes annual recommendations for the composition of the vaccine against
the influenza strain for the upcoming winter season. The vaccines
are composed of two A strains (H1N1 and H3N2) and a B strain. The
1998-1999 preparation, for example, consists of the following strains:
A/Beijing/262/95 (H1N1), A/Sydney/5/97-like (H3N2), and B/Harbin/7/94.
They are available as whole inactivated vaccines, split-virion, or subunit.
Manufacturers include: Connaught Laboratories, Inc. (Fluzone, whole or
split); Evans Medical Ltd (Fluvirin, purified surface antigen vaccine);
and Wyeth-Ayerst Laboratories (Flushield, split). The appropriate
influenza viruses are propagated separately in chicken embryos, then harvested
and inactivated with formaldehyde. They are purified using a linear
sucrose density gradient solution. Thimerosal is used as a preservative.
To create a split-virion vaccine, the virus is then chemically disrupted
using ether, and it is further purified through chemical means and suspension.
Purified surface antigen vaccines are composed of purified HA and NA glycoproteins.
Vaccines must be kept refrigerated.
Dosage
The vaccine is available in September for the upcoming winter.
The vaccine should be administered intramuscularly, injected preferably
in the deltoid muscle for adults and children, and the thigh for infants.
Children under the age of 9 should be administered the split-virion vaccine
to lower the possibility of febrile reactions. They should receive
two doses one month apart to maximize the antibody response. Infants
below the age of 35 months (but older than 6 months) receive 0.25 ml of
the split virus formula, while older individuals are adminstered 0.50 ml
of any of the vaccine types. The effectiveness of the vaccine decreases
with the age of the vaccinee. It decreases the occurrence of influenza
by 70-90% in individuals younger than 65 years. For the elderly,
the vaccine is most effective in preventing secondary infections, such
as pneumonia, and decreasing hospitalization and mortality associated with
an influenza infection at an old age. Influenza illness may be decreased
by only 30-40% in the elderly, yet hospitalization for serious complications
is cut by 80%.
Side Effects and
Precautions
The inactivated vaccine cannot cause infection. The most frequent
side effect is soreness at the vaccination site for up to two days.
Systematic reactions may occur in young children who have had no previous
exposure to the influenza virus antigens in the vaccine; these include:
fever, malaise, and myalgia. While the 1976 vaccine produced a heightened
incidence of Guillain-Barre syndrome, the association has not been reported
since then. Individuals allergic to eggs or egg products must not
receive the vaccine. Those who are sensitive to the preservative
thimerosal should avoid the vaccine as well.
Who Needs It?
The vaccine is highly recommended for individuals older than 65, residents
of nursing homes, those with chronic disorders of the pulmonary or cardiovascular
systems (e.g. asthma), those with chronic metabolic diseases, children
who are receiving long-term aspirin therapy and might be at risk for developing
Reye syndrome, and women in the second or third trimester of pregnancy
during influenza season. People who can potentially transmit influenza
to high-risk groups should be vaccinated as well; these include hospital
personnel, employees of nursing homes, and household members of people
in high-risk groups. Individuals within the general population should
receive the vaccine if they wish to reduce the likelihood of becoming ill.
Those in institutional settings (e.g., students in dormitories, military
personnel in barracks) are encouraged to use the vaccine.
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Japanese encephalitis (JE) is a mosquito-borne arboviral disease of significant
public health concern in Asia; after HIV, it may be the leading cause of
viral encephalitis worldwide. The majority of infections are actually
asymptomatic; only 1 in 25-1000 infection produces symptoms. Incubation
is 5-15 days, and illness usually begins with an abrupt onset of high fever,
change in mental status and headache, followed gradually by disturbances
in speech, gait or other motor dysfunctions. In children, the disease
begins with irritability, acute convulsions, and gastrointestinal symptoms
of anorexia, nausea, abdominal pain, vomiting and diarrhea. Loss
of altertness and responsiveness eventually leads to coma and death in
25% of symptomatic cases. Young children are more likely to die.
A third of surviving patients are left with permanent residual neurological
disability.
Vaccine Preparation
The primary viruses used are the Beijing-1 and Nakayama strains.
Inactivated JE virus produced in mouse brain is available for worldwide
distribution. Inactivated JE vaccine is distributed internationally
by Biken and the Korean Green Cross. In the U.S., the Biken vaccine
is distributed by Connaught Laboratories as JE-Vax. After growth
in mouse brain, centrifugation, ultrafiltration, protamine sulfate precipitation,
and formalin inactivation in cold, followed by further purification by
ultrafiltration, ammonium sulfate precipitation and continuous zonal centrifugation
on sucrose density gradients purify the virion. The vaccine is diluted
with medium 199 and phosphate buffer, then stabilized with gelatin, sodium
glutamate, and thimerosal. It remains stable at 4o C for
up to a year.
Dosage
For adults and children over 3, the recommended dose is 1.0 ml administered
subcutaneously on days 0, 7, and 30, followed by boosters after one year,
then every three years. For children under 3, the dosage is 0.5 ml
with a similar time schedule. Seroconversion occurs in 95% of vaccinees.
Side Effects and
Precautions
Local tenderness, redness, or swelling at the
injection site occurs in approximately 20% of vaccinees. 10-30%
of vaccinees report mild systemic symptoms, chiefly headache, low grade
fever, myalgias, malaise, and gastrointestinal symptoms. Allergic
reactions, including urticaria and angioedema, have been associated with
JE vaccine produced in mouse brain.
Who Needs It?
Japanese encephalitis is rare in the United States, so is unecessary
for non-travelling citizens. The JE vaccine is recommended for travellers
to rural areas of Asia. For individuals travelling to urban areas,
the vaccination is quite unnecessary because the presence of JE within
city boundaries is extremely low. Immunization is recommended for
visitors to endemic areas during the transmission season, and for those
at high risk of exposure to the mosquito vector, such as workers and consultants
on construction, agricultural, or other field projects in rural areas.
Laboratory workers in contact with the virus should receive vaccination.
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The virus is spread via the respiratory transmission route. The
clinical manifestation involves fever, cough, coryza, conjunctivitis, and
a characteristic maculopapular rash that appears on the head and spreads
progressively over the chest, trunk, then limbs. Immunologically
deficient children can die from measles-induced pneumonia or from acute
progressive infectious encephalitis. The most dangerous complication
of measles, and a major reason for the administration of its vaccine, is
acute postinfectious encephalitis, occurring in about 1 in every 1000 cases
with a mortality rate of 15%. Subacute sclerosing panencephalitis
(SSPE) is much rarer. It develops in 1 in every 300,000 cases years
after apparent recovery from original infection. Vigorous immunization
in the U.S. has led to the loss of indigenous measles.
Preparation and
Storage
A live vaccine was first introduced in 1963 by Enders then modified
to produce the Schwarz vaccine used presently. The vaccine is derived
from Enders' original Edmonston strain. It is prepared in chick
embryos, and is highly attenuated. Produced by Merck, the vaccine
(Attenuvax) is available in monovalent form, and more commonly in the measle-mumps-rubella
(MMR) combination. Each 0.5 ml dose contains 1000 TCID50
(tissue culture infectious doses--a unit of measurement) of the U.S. Reference
Measles Virus; 20,000 TCID50of the Mumps virus; and 1000 TCID50
of
the Rubella virus. Each dose contains 25 ug of neomycin and is stabilized
with sorbitol and hydrolized gelatin. The MMR vaccine is lyophilized
(freeze-dried) and is reconstituted immediately before administration.
It must be maintained at 10o C or less.
Dosage
The dosage of the combination MMR vaccine is the same for all vaccinees:
0.5 ml. A diluent is added to the lyophilized vaccine before injecting
subcutaneously. Immunization is recommended for patients older than
15 months; younger infants may develop a suboptimal response due to the
presence of maternal antibodies. At least 95% of recipients develop
an effective antibody response against each virus after one dose.
It is recommended that children receive a booster of the monovalent or
polyvalent vaccine prior to entering kindergarten (4-6 years of age) or
junior high school (11-12 years).
Side Effects and
Precautions
Because the MMR vaccine is composed of live viruses, side effects can
be quite numerous. Burning and stinging at the injection site have
been reported after administration of the MMR vaccine. Systematic
symptoms include malaise, sore throat, cough, rhinitis, headache, diziness,
fever, rash, nausea, arthritis, vomiting or diarrhea. Local reactions
include erythema, induration, regional lymphadenopathy. There may
be instances of parotits, orchitis, nerve deafness, thrombocytopenia and
purpura. Allergic reactions to the egg components have been reported.
Conjunctivitis and optic neuritis may occur. Moderate or high fevers
may ensue. The MMR vaccine must not be given to pregnant women, and
pregnancy must be avoided for at least three months after vaccination.
MMR must not be administered to patients with febrile respiratory illness,
active tuberculosis, those receiving immunosuppressive therapy, individuals
with leukemia or lymphomas. This vaccine must be given one month
before or after the administration of any other vaccine.
Who Needs It?
In the U.S., a measles vaccination is required of all children to enter
the educational system. Those who cannot readily provide 1) a physician-documented
history of measles, 2) laboratory evidence of measles immunity or 3) a
documented history of vaccination with live measles virus vaccine on or
after the first birthday should be vaccinated or excluded from school.
People who have only received one vaccination as an infant are encouraged
to receive a booster. International travellers should consider revaccination,
and laboratory workers exposed to the virus should be administered the
vaccine as well.
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Mumps is transmitted by direct contact with saliva or aerosolization.
The disease involves the painful edematous enlargement of parotid and other
salivary glands. The afflicted individual is unable to eat or talk
without discomfort. Other glands may be involved, including the pancreas,
ovary, thyroid, and breast. Epididymoorchitis (swollen testis) is
a dangerous situation that occurs in 25% of mumps cases in postpubertal
males which may lead to testical atrophy and permanent sterility.
10% of cases result in benign meningitis. Encephalitis is a less
frequent, but more serious ailment, leading to possible nerve deafness.
Mumps infection in infants is usually asymptomatic or presents itself as
a respiratory syndrome.
Preparation and
Storage
The vaccine is composed of a live, attenuated virus, marketed by Merck
as Mumpsvax. The Jeryl Lynn strain is grown in cell cultures of chick
embryo and then properly attenuated. In the U.S., it is often administered
in a trivalent vaccine containing, mumps, measles, and rubella virion (MMR).
Each 0.5 ml dose contains 1000 TCID50 (tissue culture infectious
doses--a unit of measurement) of the U.S. Reference Measles Virus; 20,000
TCID50of the Mumps virus; and 1000 TCID50 of the
Rubella virus. Each dose contains 25 ug of neomycin and is stabilized
with sorbitol and hydrolized gelatin. The MMR vaccine is lyophilized
(freeze-dried) and is reconstituted immediately before administration.
It must be maintained at 10o C or less.
Dosage
The dosage of the combination MMR vaccine is the same for all vaccinees
regardless of age: 0.5 ml. A diluent is added to the lyophilized
vaccine before injecting subcutaneously. Immunization is recommended
for patients older than 15 months; younger infants may develop a suboptimal
response due to the presence of maternal antibodies. At least 95%
of recipients develop an effective antibody response against each virus
after one dose. It is recommended that children receive a booster
of the polyvalent vaccine prior to entering kindergarten (4-6 years of
age) or junior high school (11-12 years).
Side Effects and
Precautions
Burning and stinging at the injection site have been reported after
administration of the MMR vaccine. Systematic symptoms include malaise,
sore throat, cough, rhinitis, headache, diziness, fever, rash, nausea,
arthritis, vomiting or diarrhea. Local reactions include erythema,
induration, regional lymphadenopathy. There may be instances of parotits,
orchitis, nerve deafness, thrombocytopenia and purpura. Allergic
reactions to the egg components have been reported. Conjunctivitis
and optic neuritis may occur. Moderate or high fevers may ensue.
The MMR vaccine must not be given to pregnant women, and pregnancy must
be avoided for at least three months after vaccination. MMR must
not be administered to patients with febrile respiratory illness, active
tuberculosis, those receiving immunosuppressive therapy, individuals with
leukemia or lymphomas. This vaccine must be given one month before
or after the administration of any other vaccine.
Who Needs It?
The ACIP recommends that all children should receive a mumps vaccine
as part of the MMR administration at 15 months of age. Also, people
who are unsure of their mumps disease history or mumps vaccination history
should be vaccinated. It may be beneficial to receive the MMR vaccination
prior to international travelling or if occupational duties require constant
exposure to mumps, measles, or rubella.
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Polio is no longer endogenous to the United States, but up through the
1950s, it was a greatly feared disease. It enters the body through
ingestion, eventually leading to viremia. The virus is subsequently
carried to the anterior horn cells of the spinal cord where the virus replicates.
The majority of infections take the form of a minor illness: fever,
malaise, sore throat, headache, vomiting, and aseptic meningitis.
In 1% of cases, paralysis ensues, possibly leading to respiratory or cardiac
failure. If the patient surives, some degree of motor function recovery
may occur over the proceeding months, but paralysis is usually permanent.
Postpolio syndrome, involving further muscle atrophy years after recovery,
may be observed in some cases.
Vaccine Preparation
Two types of vaccines are in use: enhanced-potency (Salk) poliovaccine
(IPV) and live attenuated (Sabin) oral poliovaccine (OPV); both are trivalent
vaccines consisting of the Mahoeny, MEF-1, and Saukett strains. IPV
is available under two brandnames: IPOL and POLIOVAX. The IPOL
vaccine consists of viruses grown, concentrated, and purified from monkey
kidney cells. After formaldehyde inactivation, each dose of vaccine
contains 40 D antigen units of type 1, eight D antigen units of type 2,
and 32 D antigen units of type 3. Trace amounts of 2-phenoxyethanol,
formaldehyde, neomycin, streptomycin, and polymyxin B are present.
The POLIOVAX vaccine is cultured on human diploid cell cultures, and consists
of the same concentration of viral strains and solvents. OPV is also
trivalent vaccine, containing attenuated strains of all three serotypes
in the ratio 10:1:3. The viruses are grown in human diploid fibroblasts
or monkey kidney cells, where they acquire several mutations during serial
passage in the cultured cells, leading to attenuation as confirmed by lack
of neurovirulence when inoculated into monkeys. Magnesium chloride
is added to protect the virus against heat inactivation.
Dosage and Administration
The AAP recommends two doses of IPV administered at ages 2 and 4 months
followed by two doses of oral poliovirus vaccine (OPV) at ages 12-18 months
and 4-6 years. The administration of IPV for all four poliovirus vaccine
is recommended for immunocompromised individuals and their household contacts.
OPV is used for the first two doses only under special circumstances (e.g.
vaccinations of children whose parents do not accept the recommended sequential
schedule, late start in the vaccination schedule, and imminent travel to
countries where polio is endemic.). OPV is administered in 0.5 ml
doses; IPV is injected subcutaneously in 0.5 ml doses. Following
this series of vaccinations, 95% of the vaccinees undergo seroconversion.
The use of OPV induces superior gastrointestinal immunity.
Side Effects and
Precautions
No serious side effects are associated with IPV other than allergic
responses to the antibiotic components. Administration of OPV has
been responsible for vaccine-associated paralysis (VAPP) in 1 out of 4
million vaccinations; the revised childhood vaccination schedule is an
attempt to decrease this occurrence. Vaccination of pregnant women,
individuals allergic to any of the vaccine contents, and those with immunodeficiency
disorders should be avoided. OPV should not be administered to individuals
who will be coming into close contact with immunocompromised people over
the following 4-6 weeks.
Who Needs It?
The ACIP and the AAP recommend IPV and OPV as part of the required
vaccination schedule of American children. Vaccination is recommended
for adults who are travelling to areas where poliomyelitis is endemic,
laboratory workers who handle specimens containing the virus, health-care
workers, and unvaccinated adults whose children will be receiving OPV.
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The disease is extremely rare in the U.S. with no more than 5 cases
per year. Rabies is typically transmitted to humans through the bite
of an infected warm-blooded animal. Speleologists can inhale the
virus shed in the feces of infected bats, and iatrogenic procedures could
potentially act as another route of transmission. A slow infection,
rabies eventually travels through the peripheral neural axons and into
the central nervous system, leading to dysphagia, hydrophobia, manic behavior
alternating with lethargy, leading to coma and death from respiratory failure.
Once the disease manifests itself, mortality is nearly 100%.
Preparation
Three inactivated vaccines are available for use within the U.S. Chiron
Behring GmbH and Company manufacture the purified chick embryo cell culuture
vaccine RabAvert. It is a freeze-dried vaccine obtained by growing
the Flury strain of rabies in cultures of chicken fibroblasts. The
virus is filtered, inactivated with b-propiolactone, then further purified
and concentrated through centrifugation. A stabilizer is added, then
the vaccine is lyophilized, and reconstituted immediately before use.
Human diploid cell rabies vaccine (HDCV) is prepared from fixed rabies
virus grown in human diploid cell culture. It is inactivated with
tri-n-butyl phosphate and B-propiolactone, and supplied as lyophilized
doses. Produced by the Michigan Department of Public Health, Rabies
Vaccine Adsorbed (RVA) is prepared from the Kissling strain of rabies virus
adapted to fetal rhesus lung cells. It is inactivated with b-propiolactone
and is adsorbed to aluminum phosphate as an adjuvant. RVA, unlike
the former two brands, is supplied as a liquid, rather than freeze-dried.
Dosage
Rabies prophylaxis can be administered before or after exposure since
the virus produces a very slow infection. When administering any
of the three available vaccines, the pre-exposure vaccination consists
of three 1.0-ml doses delivered intramuscularly on days 0, 7, 21 or 28.
Postexposure vaccination involves five 1.0-ml doses injected intramuscularly
on days 0, 3, 7, 14, and 28. A dose (20 IU per kg of body weight)
of human rabies immune globulin (HRIG) should be used to wash the wound
and also injected into the patient. For those who have had previous
rabies vaccination, postexposure prophylaxis consists of two 1.0-ml doses
on days 0 and 3; HRIG should not be administered. The vaccination
lowers the risk of mortality to practically zero.
Side Effects and
Precautions
Local reactions include swelling, induration, reddening, pain, and
itching among 25% of the vaccinees. Systematic reactions include
headache, nausea, abdominal pain, muscle aches, and dizziness in 20% of
recipients. Among those receiving booster doses, cases of arthralgia,
arthritis, angioedema, nausea, vomiting, fever, and malaise have been reported.
Two cases of neurologic illness resembling Guillain-Barre syndrome have
been reported.
Who Needs It?
The pre-exposure vaccination is reserved largely for those who handle
animals or the rabies virus on a regular basis. These include lab
workers, spelunkers, veterinarians, animal control and wildlife workers.
The postvaccine regimen must be followed by those who have been bitten
by a domestic animal that is known to have or soon develops rabies symptoms.
Those who are bitten by escaped domestic animals or wild aniimals should
seek vaccination.
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Rotavirus is spread through fecal-oral transmission. Predominantly
a childhood infection, rotavirus virtually infects all children at least
once by the time they are three. It produces clinical illness largely
between the ages of 6 and 24 months; neonates remain largely asymptomatic.
Following a very short incubation period (1-3 days), vomiting precedes
severe diarrhea, lasting for up to 5 days. Each year in the United
States, rotavirus is responsible for approximately 500,000 physician visits
and 50,000 hospitalizations (30-50% of all hospitalizations for diarrhea
in children under 5 years of age). Deaths are uncommon in the U.S.
and other developed nations. Children in third world countries suffering
from malnourishment and other disease complications often succumb to dehydration
and die.
Vaccine Preparation
FDA approval for the rotavirus vaccine was very recent, occurring on
August 31, 1998. Prepared by Wyeth-Ayerst, RotaShield is a live,
attenuated tetravalent vaccine. The vaccine is derived from an attenuated
rhesus monkey rotavirus strain (RRV-1 or MMU18006) grown in tissue culture,
and is antigenically similar to the human serotype 3. Three additional
strains of RRV-1 have been developed that contain antigenic VP7 genes from
the other human rotavirus serotypes (1, 2, and 4) commonly found in the
United States. The vaccine is supplied in boxes of 12 doses as lyophilized
powder in individual-dose bottles and 12 individual droppers with pre-measured
diluent.
Dosage
Rotavirus vaccine is administered orally to infants at ages 2, 4, and
6 months as 2.5-ml reconstituted doses. The three-dose series should
be completed by the first birthday. The first dose should not before
6 weeks or later than seven months, and the minimum interval between doses
is 3 weeks. It confers 49% to 68% protection against any rotavirus
diarrhea and 61% to 100% protection against severe disease.
Side Effects and
Precautions
In clinical trials, infants aged 6 months or older had a higher incidence
of fever after the receipt of the first rotavirus vaccination. This
may be due to the decreased concentration of maternal antibodies.
Who Needs It?
The recent FDA approval of the rotavirus vaccine and the AAP and the
ACIP recommendation to include it as part of the childhood immunization
schedule have created some level of uncertainty among physicians and parents.
In the U.S., rotaviral infections rarely lead to deaths (<300 per year).
If the child is kept properly nourished, the disease is relatively benign.
The implementation of the vaccine is driven largely by its economic benefits;
it can potentially decrease the number of hospitalizations, thereby decreasing
the financial burden imposed on medical institutions, insurance companies,
and society at large. In terms of personal well-being, however, the
decision to receive a vaccination lies mainly with the child's parents
and physician.
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The virus is spread through a respiratory route of transmission.
In children, the disease is quite mild. The erythematous rash first
appears as fine, pink, discrete macules on the face, then spread to the
trunk and limbs, and disappear after 48 hours. Half of all infections
produce no rash; however, almost all infectiosn result in swollen postauricular,
suboccipital, and posterior cervical lymph nodes. Adult females frequently
develop arthritis. Postinfectious encephalopathy is a rare complication.
Progressive rubella panencephalitis is even rarer; it is fatal, develops
in the second decade of life, and is usually in children with congenital
rubella. 20% of infants infected in utero during the first trimester
of pregnancy develop severe congenital abnormalities such as deafness,
blindness, heart disease, and mental retardation.
Vaccine Preparation
Merck produces Meruvax II, the Wistar RA 27/3 strain of live attenuated
rubella virus grown in human diploid cell culture. It is most often
administered as part of the combined measles-mumps-rubella vaccine (MMR)
introduced in 1972. Each 0.5 ml dose contains 1000 TCID50
(tissue culture infectious doses--a unit of measurement) of the U.S. Reference
Measles Virus; 20,000 TCID50of the Mumps virus; and 1000 TCID50
of
the Rubella virus. Each dose contains 25 ug of neomycin and is stabilized
with sorbitol and hydrolized gelatin. The MMR vaccine is lyophilized
(freeze-dried) and is reconstituted immediately before administration.
It must be maintained at 10o C or less.
Dosage
The dosage of the combination MMR vaccine is the same for all vaccinees
regardless of age: 0.5 ml. A diluent is added to the lyophilized
vaccine before injecting subcutaneously. Immunization is recommended
for patients older than 15 months; younger infants may develop a suboptimal
response due to the presence of maternal antibodies. At least 95%
of recipients develop an effective antibody response against each virus
after one dose. It is recommended that children receive a booster
of the polyvalent vaccine prior to entering kindergarten (4-6 years of
age) or junior high school (11-12 years).
Side Effects and
Precautions
Burning and stinging at the injection site have been reported after
administration of the MMR vaccine. Systematic symptoms include malaise,
sore throat, cough, rhinitis, headache, diziness, fever, rash, nausea,
arthritis, vomiting or diarrhea. Local reactions include erythema,
induration, regional lymphadenopathy. There may be instances of parotits,
orchitis, nerve deafness, thrombocytopenia and purpura. Allergic
reactions to the egg components have been reported. Conjunctivitis
and optic neuritis may occur. Moderate or high fevers may ensue.
Although the teratogenic effects of the vaccine have not been substantiated,
prudence dictates that the MMR vaccine must not be given to pregnant women,
and pregnancy must be avoided for at least three months after vaccination.
MMR must not be administered to patients with febrile respiratory illness,
active tuberculosis, those receiving immunosuppressive therapy, individuals
with leukemia or lymphomas. This vaccine must be given one month
before or after the administration of any other vaccine.
Who Needs It?
The mumps vaccine, as part of the MMR combination, is recommended by
the ACIP as part of the routine immunization schedule for all children
within the United States. Women are highly advised to be immunized,
if they have not yet done so, to decrease the likelihood of becoming infected
during pregnancy resulting in congenital abnormalities of the developing
fetus.
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Varicella-Zoster virus (VZV) is transmitted through the respiratory
tract. Largely a childhood disease, chickenpox often appears suddenly
as a rash erupting first on the trunk then spreading to the head and limbs.
The vesicles become pustules then scabs. The lesions are very itchy.
Ulcerating vesicles can also occur on mucous membranes. Adults who
develop the disease are more likely to succumb to life-threatening varicella
pneumonia. In 1/1000 cases, encephalitis develops shortly after teh
appearance of the rash. In immunocompromised individuals, the disease
can become particularly dangerous as the infection disseminates to several
internal organs. Varicella infection in pregnant woman has been shown
to produce congenital malformations in the fetus. Zoster results
from reactivation of virus that has remained latent in sensory ganglia
after a chickenpox infection many years earlier. The unilateral vesicles
are confined to the area of the skin innervated by a particular sensory
ganglion, uusually on the trunk or on the face. The pain is very
severe and may persist for several weeks. In patents over 60, it
may last for many months.
Vaccine Preparation
The varicella virus vaccine available in the United States consists
of the Oka strain of live, attenuated VZV. It was isolated in Japan
in the 1970s from a healthy child who had natural varicella. The
virus was attenuated through sequential propagation in human embryonic
lung cells, embryonic guinea-pig cells, and human diploid cells (MRC-5).
The virus undergoes an additional 31 passages through human diploid cel
cultures. Each 0.5 ml of the reconstituted lyophilized vaccine (Varivax
by Merck) contains 1,350 plaque forming units (PFUs) of Oka VZV, 12.5 mg
hydrolyzed gelatin, 25 mg sucrose, and trace amounts of neomycin, bovine
serum and MRC-5 cells.
Dosage
After reconstitution, 0.5 ml is injected intramuscularly. One
dose is recommended for children between the ages of 12 months and 13 years
if they have not yet developed chicken pox. Patients over the age
of 13 should receive two doses 4 to 8 weeks apart. The varicella
virus vaccine provides 70%-90% protection against infection and 95% protection
against severe disease for up to 10 years after vaccination.
Side Effects and
Precautions
Pain and redness at the injection site were the common side effects
of vaccination. 14.7% developed fever, and no more than 4% experienced
either a local or systemic varicella-like rash of no more than five lesions.
The vaccine should not be administered to those who have allergic responses
to gelatin, neomycin, or other components of the vaccine. It should
not be used for immunosuppressed patients, those suffering from any severe
illness, or pregnant women.
Who Needs It?
While chicken pox is a relatively benign disease among children, it
has been recommended that all infants 12-18 months of age be vaccinated.
Children over the age of 12 months but under 13 years should receive the
vaccination if they have not been exposed to the natural virus, and are
therefore susceptible to natural infection. If they do not have a
reliable history of varicella exposure, adults over the age of 13 should
be vaccinated if they have close contact with people at high risk for serious
complications, teachers of young children, day-care employees, college
students, thoise in institutional setting, nonpregnant women, international
travelers, and health care workers.
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Yellow fever is an arthopod-borne disease, limited to endemic areas
of Africa and South America. The virus replicates within the Kupffer
cells of the liver, leading to massive death of these cells and jaundice.
Most cases are mild, presented as fever, chills, headache, backache, mayalgia,
and vomiting. A few cases progress to severe jaundice, massive gastrointestinal
hemorrhaging, low blood pressure, dehydration, and kidney failure.
Up to 50% of people who develop this more severe form will die.
Vaccine Preparation
The vaccine is a live, attenuated virus prepared from the 17D yellow
fever virus strain. It is grown in chick embroyos, purified, centrifuged,
then freeze-dried. The vaccine should be kept frozen until ready
to use, at which point a sterile diluent is used as a reconstituent.
Dosage
For people of all ages, one subcutaneous injection of 0.5 ml is administered.
Boosters are required at 10-year intervals. Studies suggest that
revaccination boosts antibody concentration, while the primary vaccination
produces an immunity that lasts for up to 35 years.
Side Effects and
Precautions
2-5% of vaccinees have reported mild headaches, myalgia, and low-grade
fevers. Among 34 million distributed doses, only two cases of encephalitis
were reported. The vaccine is not intended for children under 9 months
of age. Pregnant women should avoid the vaccine. Immunosuppressed
individuals or patients with allergies to egg products must not receive
the vaccination. It is safe to administer it concurrently with all
vaccines other than cholera. The two vaccines should be given at
least 4 weeks apart.
Who Needs It?
The 17D yellow fever vaccine is intended primarily for international
travelers. It should be given to anyone over the age of 9 months
who will be traveling to areas where yellow fever is endemic, such as South
America and Africa. Laboratory workers who may be exposed to the
virus should be vaccinated as well.
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