SMALLPOX VACCINE (DRYVAX)
Smallpox vaccine is live vaccinia (cowpox) virus grown on the skin of a bovine calf. Smallpox is a highly lethal and disfiguring disease that was common throughout history. Smallpox vaccine was used routinely in the United States but today is no longer recommended. (There have been no reported cases of smallpox since the 1940s.) In 1982, smallpox was declared eradicated worldwide. With smallpox, the risks of the vaccine outweigh the benefits; the vaccine penetrates the central nervous system and potentially fatal encephalitis occurs in 1 of l05 patients. After exposure to smallpox, the vaccine can be injected to lessen the severity of the disease.
Influenza vaccine is a multivalent inactivated influenza virus or viral subunits (split vaccine). The virus is grown on chick embryo and inactivated by exposure to ultraviolet (UV) light or formaldehyde. The antigen type is protein. The vaccine in the United States contains thimerosal, a mercurial, as a preservative. Influenza is a respiratory tract infection with a 2-day incubation period. The disease may be devastating and can lead to pneumonia. Without the vaccine, influenza is common in epidemics and pandemics. To clarify, the flu is a GI infection with diarrhea and vomiting. Influenza requires weeks of incubation. Influenza is caused by two main genetic strains each year (A and B): type A is most common in humans; type B is less common. The virus mutates very rapidly, and vaccines must be tailored yearly. The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) monitor the migration of the disease from Southeast Asia, type the strains causing the occurrences, and order a vaccine to counter the organisms most likely to enter the United States. Influenza A viruses are categorized according to two cell surface protein antigens: hemagglutinin (H) and neuraminidase (N). Each of these is divided further into subtypes (H1, H2; N1, N2). Individual strains within a subtype are named for the location, isolation sequence number, and year of isolation (e.g., A/Beijing/2/90 [H1N1]). For example, the WHO-recommended formula for 2001 to 2002 included the following antigens: A/New Caledonia/20/99 (H1N1), A/Moscow/10/99 (H3N2), B/Sichuan/379/99, 15 ^g each per 0.5 mL. A typical vaccine will be a mixture of three strains. Strains are selected each year in the spring on the basis of the disease trends observed and are released in the autumn. In general, those patients who are at high risk for complications from influenza are the following:
• Persons 65 years of age or older
• Residents of nursing homes and other chronic-care facilities that house persons of any age who have chronic medical conditions
• Adults and children who have chronic disorders of the pulmonary or cardiovascular systems, including asthma
• Adults and children who have required medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes melli-tus), renal dysfunction, hemoglobinopathies, or immuno-suppression (including immunosuppression caused by medications or HIV infection)
• Children and teenagers (aged 6 months-18 years) who are receiving long-term aspirin therapy and, therefore, might be at risk for developing Reye syndrome after influenza infection
• Women who will be in the second or third trimester of pregnancy during the influenza season
• Healthcare workers and those in close contact with persons at high risk, including household members
• Household members (including children) of persons in groups at high risk, including persons with pulmonary disorders, such as asthma, and healthcare workers who are at higher risk because of close contact
It is impossible to contract influenza from the vaccine. The only side effects may be local pain and tenderness at the injection site, with low-grade fever in 3% to 5% of patients. Aspirin and acetaminophen are effective in combating these symptoms. Allergic reactions are rare but may be seen in persons allergic to eggs. Immunity to influenza vaccine takes 2 weeks to develop. Some people fear the vaccine because of reports of a strange paralysis and lack of nerve sensation associated with the 1976 swine flu vaccine. This problem, Guillain-Barre syndrome, was associated only with this 1976 vaccine and has not been associated with vaccines since.17
Polio is a dangerous viral infection that affects both muscle mass and the spinal cord. Some children and adults who contract polio become paralyzed, and some may die because of respiratory paralysis. Polio was the cause of the "infantile paralysis" epidemic of 1950 to 1953, which led to many paralyzed children and the specter of patients spending their lives in an iron lung. Serious cases of polio cause muscle pain and may make movement of the legs and/or arms difficult or impossible and, as stated previously, may make breathing difficult. Milder cases last a few days and may cause fever, sore throat, headache, and nausea. Interest in polio has increased because of recent local outbreaks; large numbers of people are unimmunized. There are no drugs or special therapies to cure polio; treatment is only supportive. The symptoms of polio may reappear 40 to 50 years after a severe infection. This phenomenon is known as postpolio muscle atrophy (PPMA). PPMA is not a reinfection or reactivation of the virus but is probably a form of rapid aging in polio survivors. There are two types of polio vaccines.
Inactivated Polio Vaccine (IPV)
There are several synonyms for the IPV vaccine: IPV, e-IPV, ep-IPV, and the Salk vaccine (1954 [IPOL, Aventis-Pasteur]). e-IPV is an enhanced potency poliovirus, more potent and immunogenic than any of the previous IPV formulations. e-IPV is recommended for all four infant doses because of the incidence of rare cases of oral polio vaccine (OPV)-associated paralytic poliomyelitis. e-IPV is also preferred for adults for the same reason. IPV is a trivalent (strains 1, 2, 3) vaccine grown in monkey kidney culture and subjected to elaborate precautions to ensure inactivation (typically, formaldehyde is used). The antigen form is whole virus. The antigen type is protein. The vaccine is injected to cause induction of active systemic immunity from polio but does not stop polio carriers, who shed the virus from the oral and nasal cavities.
Trivalent Oral Polio Vaccine (TOPV)
TOPV (Sabin vaccine, 1960) is a live attenuated whole virus vaccine (antigen type, protein) containing polio strains 1, 2, and 3. The virus culture is grown on monkey kidney tissue with the use of an elaborate attenuation protocol. Oral administration of the vaccine yields a local GI infection, and the initial immune response is via IgA (mucosal, local to the GI tract). The IgA-antigen complex undergoes transcytosis across the mucosal membrane, and systemic immunity is induced as IgM and IgG form. A major caution with TOPV is that it is a live vaccine and must never be injected. Indications are the following:
• Mass vaccination campaigns to control outbreaks of paralytic polio.
• Unvaccinated children who will travel in less than 4 weeks to areas where polio is endemic.
• Children of parents who do not accept the recommended number of vaccine injections. These children may receive OPV only for the third or fourth dose or both. In such cases, the healthcare provider should administer OPV only after discussing the risk of OPV-associated paralytic poliomyelitis with parents or caregivers.
• e-IPV is recommended for routine use in all four immunizing doses in infants and children.
• The WHO has advocated giving children e-IPV instead of TOPV to prevent exposure of others to virus shed through the nose and mouth.21,22
German measles is a disease that was once called the "3-day measles" and was considered a normal childhood illness. It is a mild disease with few consequences, except in the first trimester of pregnancy. In these mothers, rubella causes birth defects in 50% of cases. Defects may include heart disease, deafness, blindness, learning disorders, and spontaneous abortion of the fetus. Symptoms of rubella are a low-grade fever, swollen neck glands, and a rash that lasts for about 3 days. About 1 of every 10 women of childbearing age in the United States is not protected against rubella. Also, 20% of all adults escaped this normal childhood disease or are not vaccinated.
Rubella vaccine (German measles vaccine, live, Meruvax II, Merck) is a live, attenuated rubella virus produced in human diploid cell culture. The antigen form of the vaccine is whole virus. The antigen type is protein. The vaccine is administered as part of the normal immunization schedule at 15 months. Side effects are minimal, but there may be some soreness and pain at the site of injection and stiffness of the joints.
A problem with the vaccine is that administration of a live virus is contraindicated in pregnancy. Indications are the following:
• Persons aged 12 months to puberty should be immunized routinely.
• Previously unimmunized children of susceptible pregnant women should receive the MMR vaccine. The trivalent vaccine is preferred for persons likely to be susceptible to mumps and rubella.
• Immunization of susceptible nonpregnant adolescent or adult women of childbearing potential is called for if precautions to avoid pregnancy are observed.
• Almost all children and some adults require more than one dose of MMR vaccine.
• On the first routine visit to the obstetrician/gynecologist, the immune status should be checked. If the woman is not immunized against rubella, the physician should administer the vaccine and stress avoiding pregnancy for 3 months.
• If the patient is already pregnant, the physician should not administer the vaccine.
• If exposure is suspected, the cord blood should be monitored for the presence of rubella antibodies.
• All unimmunized women should be vaccinated immediately after delivery of the baby.
MEASLES VACCINE (ATTENUVAX, MERCK)23
Measles is a very serious, highly contagious disease. It causes a high fever, rash, and a cough lasting 1 to 2 weeks. Some patients experience extreme sensitivity to light. The rash may occur inside the eyelids, producing a very painful condition. In the United States, between 3,000 and 28,000 cases occur each year, depending on factors such as weather and localized outbreaks. Outbreaks are very common in neighborhoods and schools. One of ten children contracting measles will develop an ear infection or pneumonia. Measles may infect the brain (encephalitis) and lead to convulsions, hearing loss, and mental disability. In the United States, 1 of every 500 to 10,000 children contracting measles dies from it. Severe sickness and death are more common in babies and adults than in elementary schoolchildren or teenagers. Measles has been linked to multiple sclerosis. In 1977, a severe epidemic occurred in the United States, and 50,000 cases were reported. Only 60% of the population was vaccinated.
Measles vaccine is composed of live/attenuated measles virus that is grown on chick embryo culture with an attenuation protocol. Indications are the following:
• Selective induction of active immunity against measles virus.
• Trivalent MMR vaccine is the preferred immunizing form for most children and many adults.
• Almost all children and many adults require more than one dose of MMR.
• Prior to international travel, persons susceptible to any of the three viruses should receive the single-antigen vaccine or the trivalent vaccine, as appropriate.
• Most persons born before 1956 are likely to have contracted the disease naturally and are not considered susceptible.
• Persons born after 1956 or those who lack adequate documentation of having had the disease should be vaccinated.
The vaccine is required by law at 15 months and again at 11 to 12 years of age. The vaccine can be administered after exposure to measles to lessen the disease severity. This is because Ab to the vaccine develops in 7 days, while the incubation period for the disease is 11 days. The vaccine should not be administered in pregnancy and should always be administered with great care to women of childbearing age. Because measles vaccine is cultivated in egg medium, care must be used in patients who are allergic to eggs and egg products. For this reason, a test dose regimen is used. The administration protocol is shown in Figure 5.11.
Mumps virus causes fever, headache, and a painful swelling of the parotid glands under the jaw. Mumps can be serious and is highly contagious. Prior to the vaccine, the disease was passed from child to child with ease. The disease runs its course over several days. Between 4,500 and 13,000 cases of mumps occur as outbreaks in the United States every year. In severe cases, mumps may cause inflammation of the coverings of the brain and spinal cord (meningitis); this occurs in about 10% of infected persons. Swelling of the brain itself occurs in 1 of 200 patients. Men may experience a painful swelling of the testicles (orchitis), which may presage sterility. Women may experience a corresponding infection of the ovaries. Male teens are often sicker than other groups of either sex. Mumps early in childhood has been linked to the development of juvenile diabetes.
The mumps vaccine (Mumpsvax, Merck) is a live, attenuated virus grown on chick embryo culture with attenuation protocols. The antigen form is whole virus. The antigen type is protein. Indications are the following:
• Induction of artificially acquired active immunity against mumps.
• Before international travel, immunize any susceptible individuals with the single-antigen vaccine or the trivalent MMR vaccine, as appropriate.
• Most children and some adults need more than one dose of MMR vaccine.
• Persons born prior to 1956 are generally considered immune.
Caution. Mumps vaccine is supplied with a diluent. Use only this diluent for reconstitution. Addition of a diluent with an antimicrobial preservative can render the vaccine inactive. The vaccine is normally administered to children at 15 months of age and again at 11 to 12 years. Because mumps vaccine is cultivated in egg medium, care used to be advised in patients allergic to eggs and egg products. Recent data show that persons who are allergic to egg and egg products fail to react to the mumps vaccine.
COMBINATION PRODUCTS (POLYVALENT VIRAL VACCINES)
If two or more vaccines are free of interference with each other, they can be administered as a mixture (polyvalent) for convenience. Examples of polyvalent viral vaccines are measles-rubella (Mr), rubella-mumps (RM), and MMR. MMR is indicated for routine immunization at 15 months (not given at <1 year unless the child has been exposed or lacks immunocompetence). This is because maternal Abs interfere with development of vaccine immunity in small children. If the MMR is given at less than 1 year, revaccination is needed at 15 months of age.
Chickenpox is caused by varicella-zoster virus. Every year, about 3.5 million people in the United States, mostly children, contract chickenpox. The incidence peaks between 3 and 9 years of age. Chickenpox causes a generalized rash, with 300 to 500 blisterlike lesions occurring on the scalp, face, and trunk. Symptoms include loss of appetite, malaise, and headache. The disease is usually benign but can lead to bacterial superinfection, pneumonia, encephalitis, and Reye syndrome. About 50 to 100 previously healthy children die of the disease. About 2% of all cases occur in adults, who have more serious symptoms than children have.
Varicella vaccine (Varivax, Merck) is derived from live virus from a child with natural varicella. The virus has been attenuated by passage through a series of guinea pig and human cell cultures. The final preparation is a lyophilized live, attenuated virus. The antigen form is whole virus. The antigen type is protein. The vaccine is well tolerated, with pain and redness at the injection site as the only side effects. The vaccine has shown tremendous success in reducing infections. Indications are the following:
• The vaccine is recommended for children 12 months to 12 years old as a single dose.
• Adults who are exposed to chickenpox should continue to receive VZIG.
Hepatitis is a complex of diseases that causes fever, nausea, abdominal pain, jaundice, liver failure, and death. There are five clinically recognized types (A, B, C, D, and E).
Hepatitis A virus (HAV; infectious hepatitis) causes an acute disease with an abrupt onset. About 15 to 50 days of incubation are required before the disease becomes clinically noticeable. The primary sign is jaundice. The disease lasts several weeks and is followed by complete recovery. Hepatitis A is transmitted when the virus is taken in by mouth. The fecal-oral route and close contact, unwashed food, and contaminated water account for most of the routes of transmission. The sexual anal-oral route is also a route of spread. Children under the age of 3 frequently have no symptoms but can transmit the disease to adults in child care centers. An injection of hepatitis A immune globulin is one way of preventing the disease but is only effective for about 30 days.
The hepatitis A vaccine (Havrix) is an inactivated preparation that is produced by propagation of the virus in cultured human diploid cells and then is inactivated with formalin. The antigen form is lysed whole viruses. The antigen type is protein. The course of immunization involves two injections over a 4-week period and a booster 12 months after the first injection. Indications are the following:
• Persons traveling outside the United States, except to Australia, Canada, Japan, New Zealand, and Western Europe
• Persons with chronic liver disease
• Persons living in an outbreak zone
• Persons who inject medications
• Persons engaging in high-risk sexual activity
• Child care workers caring for children younger than 2 years of age
• Developing countries with poor sanitation
Side effects are minor and usually limited to soreness at the injection site and fever.
HBV, the cause of serum hepatitis, is a much more insidious, chronic disease, transmitted by needles, mucosal contact, blood, or high-risk sexual activity. The highest risk for contraction of hepatitis B is among intravenous drug abusers. The disease is linked to cirrhosis and liver cancer. There are about 200,000 new cases reported per year in the United States; of these, 10% become carriers, one fifth die from cirrhosis, and 1,000 die from liver cancer. The hepatitis B vaccine was first introduced in 1981. Initially, it was prepared as an inactivated vaccine from the plasma of carefully screened human, high-titer carriers/donors. In 1986, the recombinant DNA (rDNA) vaccine (Engerix B, Recombivax) was introduced to the market. The rDNA vaccine contains only viral subunits and may be used with hepatitis B immune globulin in a postexposure setting to boost the ability of the host to resist the infection. In adults, three doses should be given, at 0, 1, and 6 months. In children, the vaccine is given at birth, 1 month, and 9 months. Administration may be delayed in premature infants whose immune systems are not fully developed. If not immunized at birth, a child should receive three doses by 18 months. If the mother tests positive for hepatitis B, the vaccine plus the immune globulin must be given at or shortly after birth. The vaccine is 95% effective and is typically without side effects. Several high-risk groups have been identified: healthcare workers, student healthcare workers, people living in high-risk environments, and dentists. They should receive a three-dose course of the vaccine. In most other cases, a physician can judge whether a patient is at high risk or not. Side effects of the vaccine are minor.
Hepatitis C virus (HCV) was once called hepatitis non-A, non-B but has been recognized as a separate entity. HCV infection is spread primarily by the parenteral route (transfusions), and unlike HBV, maternal-fetal and sexual transmission are uncommon. Acute infection may show few symptoms; fewer than 25% of patients develop full-blown hepatitis. Administration of interferon alpha (IFN-a) during the early acute phase can cure most patients. Unfortunately, 50% to 60% of those with HCV infection develop chronic hepatitis. This is often manifested by periodic increases in hepatic enzyme levels. Cirrhosis develops in 20% of chronic infectees; this usually requires 15 to 20 years to develop. Patients with HCV are at risk for hepatocellular carcinoma. Estimates are that 150,000 to 170,000 new cases occur in the United States per year. Intravenous drug users, transfusion patients, and healthcare workers are at highest risk.
Development of an HCV vaccine proved difficult but was accomplished in 1998. There are 15 genotypes, and the virus can modulate its antigens within the host's body. A new approach using genetic material from the virus, analogous to the approach to the influenza vaccine, is said to be
Hepatitis E virus (HEV) causes disease clinically indistinguishable from hepatitis A. Symptoms include malaise, anorexia, abdominal pain, arthritis-like symptoms, and fever. Distinguishing HEV from HAV must be done genetically. The incubation period is 2 to 9 weeks. The disease is usually mild and resolves in 2 weeks, with no sequelae. The fatality rate is 0.1% to 1%, except in pregnant women where the rate soars to 20%. No outbreaks have been reported in the United States as of 1996. There is currently no vaccine against HEV.
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