Changes in Vaccine Practices for Children - December 2006

Over the past year, outbreaks of the vaccine-preventable diseases measles and mumps in the United States reminded us of the important role pediatricians play in maintaining the public health. The following is an overview of this year’s changes in vaccine practices for children.

Meningococcus
A tetravalent meningococcal conjugate vaccine (MCV4) was licensed for use in January 2005. The CDC recommended routine vaccination of children at age 11 to 12 years, or before entry to high school, military barracks or college dormitories if not previously vaccinated. In May 2006, the CDC and American Academy of Pediatrics recommended deferral of the vaccination in children ages 11 to 12 years because of supply limitations. In November of this year, the supply problems resolved. The CDC recommended resuming administration of the vaccine, including recall of patients who were deferred during the supply limitation.

After the CDC reviewed reports of Guillain-Barré syndrome (GBS) in recipients of the MCV4 vaccine, they did not find sufficient reason to change their recommendations. The original recommendation to withhold MCV4 vaccine from patients with a history of GBS remains.

Pertussis
In the United States, pertussis is the most prevalent vaccine-preventable disease in children. Since a nadir in 1976, the incidence of pertussis has been steadily increasing. Community pertussis rates can remain high despite high childhood vaccination rates. Because vaccine-induced pertussis immunity wanes five to ten years after vaccination, adolescents and adults in the general community act as a reservoir for the causative organism Bordetella pertussis. In 2004, the 10- to 18-year-old age group had the highest rates of reported pertussis—about 6,500 cases, or about one quarter of all cases nationwide. This reservoir of infected people presents a danger to infants who have not received sufficient vaccine to induce immunity.

In February 2006, increases in pertussis incidence across the country prompted the CDC to recommend a routine dose of tetanus-diphtheria-pertussis [Tdap] vaccine to patients 11 years of age and over. The measure in part aims to reduce the community prevalence of pertussis and thus the danger to infants. The CDC’s Advisory Committee for Immunization Practices (ACIP) recommends the Tdap vaccine to replace the typical booster of tetanus-diphtheria (Td) vaccine in adolescents and adults. In teens who have already received the Td booster, they recommend a dose of Tdap despite an increased risk for local or systemic side effects when given less than five years after the Td booster. The CDC recommends giving the Tdap booster and the meningococcal vaccine MCV4 together (both contain diphtheria toxoid) at the routine 11- to 12-year-old visit.

Rotavirus
The CDC estimates that rotavirus costs the United States one billion dollars a year. In August 2006, the CDC recommended a live oral rotavirus vaccine to add to the typical infant 2, 4 and 6 month scheduled vaccines. Natural rotavirus infection protects against subsequent severe infections but does not prevent subsequent mild infections: similarly, the rotavirus vaccine is expected to prevent severe disease but not all rotavirus gastroenteritis.

A rhesus-based rotavirus vaccine in 1998 was withdrawn after it was linked to intussusception. In a study of over 70,000 children, the new human-bovine reassortant vaccine was not linked to increases in intussusception, death or other serious outcomes. The new vaccine is not recommended for children over 32 weeks of age because of insufficient safety and efficacy data. Like other live vaccines, immune deficiency or recent administration of an antibody-containing medication affect recommendations for administration of the vaccine.

Human Papilloma Virus (HPV)
In June 2006, the ACIP made provisional recommendations for girls to receive three doses of a quadrivalent HPV vaccine scheduled for ages 11-12 years, though the vaccine can be given to girls as young as 9 years old. Catch-up vaccines are recommended for girls and women 13 to 26 years of age, preferably before their first sexual encounter. The second and third doses are given 2 and 6 months after the first dose.

The HPV vaccine will be the first vaccine expected to prevent a type of cancer: cervical cancer is the second most common cancer in women worldwide and kills 3,700 women per year in the U.S. Efficacy studies showed nearly 100% efficacy in preventing precancerous cervical, vaginal and genital lesions (as well as genital warts) due to the four strains included in the vaccine. The vaccine does not change cervical cancer screening requirements for sexually active females. It can be given to females with an abnormal or equivocal Pap test, genital warts or other evidence of HPV infection. Testing for HPV is not recommended before vaccine administration: serology tests for detecting past HPV infection are unreliable and widespread testing would reduce the cost-effectiveness of the vaccine. The CDC projects final confirmation of the ACIP provisional recommendations before the end of 2006.

Varicella
In June 2006, the ACIP made provisional recommendations for all people who have not had natural varicella infection to receive two doses of varicella vaccine. Current recommendations for children under 13 years of age are similar to those for the measles-mumps-rubella vaccine—one dose at 12 to 15 months of age and one dose at 4 to 6 years of age. They recommend a second dose to all people who have already had one dose and have not had natural varicella infection. They recommend a minimum of three months between doses for children under age 13 years, though those patients who have already received two doses are considered “validly” vaccinated if the doses were separated by 28 days or more. For children ages 13 years and older, two doses of varicella vaccine can be scheduled 4 to 8 weeks apart. The CDC projects final confirmation of the ACIP provisional recommendations in January 2007.

Consistent with the maxim “an ounce of prevention is worth a pound of cure,” current research continues to expand our fund of childhood vaccines. Between 2006 and 2015, we expect new vaccines targeted for administration to adolescents to prevent infections from herpes simplex virus (currently in large phase III trials), cytomegalovirus, chlamydiae and group B streptococcus (S. agalactiae).

References
All information noted above is publicly available at the CDC Web site. Up-to-date reports of vaccine recommendations are always available online at http://www.cdc.gov/nip/recs/provisional_recs/ .

This information provided by Tim Nicholls, M.D., Pediatric Hospitalist Program, California Pacific Medical Center Department of Pediatrics.