Vaccine update 2010: Keeping up with the changes

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Seasonal influenza vaccine extended to ages 5–18

Gradually, we seem to be moving toward vaccinating everyone every year against seasonal influenza. Previously, vaccination was recommended for children age 6 months through 4 years; in 2008, the Advisory Committee on Immunization Practices (ACIP) extended the recommendation to the age group 5 through 18 years.3

Two types of seasonal influenza vaccine are available: trivalent influenza vaccine (TIV), which contains killed virus and is given by injection, and live-attenuated seasonal influenza vaccine (LAIV), which is given by nasal spray. Both contain the same three seasonal influenza antigens, selected each year by a team of experts. TIV is licensed for those age 6 months and older, and LAIV is licensed for ages 2 through 49 years.4

Since LAIV contains a live-attenuated virus, it should not be used in anyone who has a chronic illness (including those under the age of 5 with recurrent wheezing, those with suppressed immunity, and those with a history of Guillain-Barré syndrome); in pregnant women; or those who have close contact with anyone who is immune-suppressed. The injection is contraindicated for those who have had a serious allergic reaction to eggs.

Children younger than 9 years should receive two doses of either type of vaccine the first year they are vaccinated. Those who receive only one dose the first year they are vaccinated should receive two doses the next year. If they fail to receive two doses in the next year, only a single dose is recommended after that. This is a slight modification of the previous recommendation that only one dose be given the second year if only one dose was given the first year.5

Hepatitis A vaccine at age 12–23 months

An inactivated hepatitis A vaccine (HepA) was first licensed in 1995; another was licensed in 1996. Recommendations for their use have been revised periodically, and their widespread use has resulted in a marked reduction in the incidence of hepatitis A virus infection.

The current recommendation is that all children be vaccinated at age 12 to 23 months. In addition, in areas of high prevalence, vaccine is recommended for older children who have not been vaccinated. Other target groups are those at higher risk of hepatitis A, including travelers to endemic areas, users of illicit drugs, and men who have sex with men.6 Indications for vaccination before travel, after exposure to hepatitis A infection, and in families of international adoptees are covered later in this paper in a discussion about vaccinations in adults.

Varicella at 12–15 months and 4–6 years, with catch-up for others

Before varicella vaccine was licensed in 1995, 4 million cases of varicella infection (chickenpox) were reported in the United States each year, resulting in thousands of hospitalizations and more than 100 deaths. The vaccine is now widely used, with a coverage rate of 88%, and it has proven to be 85% effective.7 The result was a marked decrease in the incidence of varicella and in varicella-related hospitalizations and deaths.

In spite of this success, the number of varicella cases has remained constant over the past few years, and sporadic outbreaks continue to occur, predominantly in schools, even schools in which a high percentage of the children are vaccinated.7,8 These outbreaks have involved infections in unvaccinated children and also “breakthrough disease” in children who have been vaccinated. If someone who has received one dose of vaccine is exposed to varicella, the risk of a breakthrough infection is about 15%.9 A two-dose series of varicella vaccine reduces the risk by about 75%.7 Breakthrough disease is usually milder than infection in the unvaccinated, with fewer skin lesions, milder symptoms, and fewer complications, but those affected are still infectious to others.

In 2005 and 2006, this ongoing risk of varicella prompted the ACIP to consider and recommend several new control measures:

  • Two doses of varicella vaccine for all children, the first dose at age 12 to 15 months and the second at age 4 to 6 years—the same schedule as for immunization against measles, mumps, and rubella
  • Two doses of varicella vaccine, the second given 4 to 8 weeks after the first, for all adolescents and adults who have no evidence of immunity
  • A catch-up second dose for everyone who received one dose previously
  • Screening for varicella immunity in pregnant women and postpartum vaccination with two doses for those who are not immune, the first dose given before discharge and the second dose 4 to 8 weeks later.

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