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Vaccine update reinforces importance of immunization
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NEW YORK — Vaccination continues to be one of the most important measures physicians can take to protect their patients from disease, according to Walter A. Orenstein, MD, who presented the keynote vaccine update at the 20th Annual Infectious Diseases in Children Symposium held here last month.
As of 2006, there has been at least a 91% decrease in morbidity for most vaccine-preventable diseases of childhood when compared with representative annual numbers of cases during the 20th century, according to Orenstein, professor of medicine and pediatrics, at Emory University, director of the Emory Vaccine Policy and Development, and associate director of Emory Vaccine Center.
During his talk, Orenstein discussed some of these benefits as they related to different vaccines, and also reviewed some of the barriers that remain in getting vaccines to children.
Herd immunity effect
Benefits of vaccine-induced community immunity are substantial, according to Orenstein.
“When you give a child vaccine, you’re not only helping that child, you’re helping your community,” he said.
Populations in whom this indirect protection is most important include children too young for vaccination, children with medical contraindications to vaccination, children who are immunocompromised and cannot make adequate immune responses, and people who do not get vaccinated.
Immunization mandates
“Immunization mandates help protect vulnerable children who are not themselves directly protected by vaccination because they assure high immunization levels in school-aged populations and decrease the chances that other susceptible children will be exposed to vaccine-preventable diseases,” Orenstein said during the presentation.
Mandates also help remove financial barriers to access by creating a societal obligation to assure all children can receive vaccines if they want them, encourage adoption by the medical community of immunization as a standard, and potentially increase the priority for vaccination among parents who are not opposed to vaccination. They also present a number of potential risks, however.
“There are risks of mandates because they galvanize anti-vaccine movements, depending on how they’re implemented,” Orenstein said.
Regardless, previously implemented mandates have demonstrated beneficial effects, according to Orenstein.
In one example, researchers examined the measles incidence in six states that strictly enforced a school vaccination mandate and compared them with the incidence of other states that did not.
Though the incidence for both groups was similar before the mandate, by 1977 there was more than a 50% decrease in incidence of measles per 100,000 children aged younger than 18 years for the states with mandates; in the first 31 weeks of 1978, researchers saw a more than 90% reduction.
Another vaccine success story has been that of the pneumococcal conjugate vaccine (PCV7; Prevnar, Wyeth), according to Orenstein.
Between 2001 and 2005, invasive disease decreased by greater than 100,000 cases as a result of the vaccine, he said. Additionally, meningitis decreased by about 2,000 cases, and pneumonia and bacteremia decreased by about 25,000 cases.
“Since many of serotypes in the vaccine accounted for a large proportion of antibiotic-resistant strains, [there has been] a major decrease in antibiotic resistance.
Concerns have been raised, however, about the increases in disease caused by serotypes not included in the vaccine.
“Among Alaska natives, these increases have counteracted the major decreases caused by vaccine serotypes,” Orenstein said in an interview. “However, serotype replacement, to date, has not been a major problem.”
Nevertheless, there have been reports of emergence of antibiotic resistant strains not currently in the PCV7 vaccine and efforts are underway to develop a vaccine that contains 13 serotypes to reduce the chances that some other types will emerge in the general population.
Although the benefits of vaccine have been apparent, there have been some problem areas, he said.
Many parents refuse vaccines because of the perceived danger in thimerosal-containing vaccines.
According to Orenstein, the Institute of Medicine’s Immunization Safety Review concluded there was a lack of evidence relating vaccines containing thimerosal to autism.
Another potentially problematic area of vaccines is potential waning immunity of certain vaccines.
Orenstein cited the recent resurgence of mumps as a possible indicator of waning immunity, but this is not definite. – by Cara Dickinson
For more information:
- Orenstein WA. Vaccines. #1. Presented at: the 20th Annual Infectious Diseases in Children Symposium; Oct. 20-21, 2007; New York.
- Maciosek MV. Priorities among effective clinical preventive services: results of a systematic review and analysis. Am J Prev Med. 2006;31:52-61.