Vaccine Safety : Part 3

by US Department of Health and Human Services

(Page 3 of 3)

Background Rates Cause Confusion

"The problem with any vaccine that's given to very young children is that there are a lot of background adverse events occurring in the first year of life," says Ellenberg.

A reaction thought to be due to a vaccine may actually have been from something else, such as an ear infection, explains Hardegree.

Children less than a year old are at greatest risk for high fevers, seizures, and sudden infant death syndrome (SIDS). These events are seen both in the presence and absence of vaccination. The SIDS death rate is approximately 1.3 per 1,000 live births during the first year of life, according to Ellenberg. During that same period, babies receive the DPT vaccine three times — at 2, 4 and 6 months.

"You don't have to be a mathematician to appreciate the fact that, by chance, SIDS will sometimes occur shortly after the vaccine was administered," says Ellenberg. "The calculations that we have been able to do suggest that the numbers of SIDS following vaccination that have been reported to VAERS are not beyond what would be expected by chance. And there have been some well-conducted, focused studies that demonstrate that SIDS is not associated with DPT vaccination. But, on the basis of VAERS data alone, we don't have proof that vaccines are not contributing to these problems and we certainly don't have proof that they are contributing."

Adding to the confusion is the fact that DPT is only one of many infant vaccines. The recommended childhood immunization schedule (192K PDF file) includes vaccines for hepatitis B, haemophilus b, measles, mumps, rubella, and polio, all during the first 12 months.

At the other end of the age spectrum, deaths are also reported after administration of the influenza vaccine. "Often these vaccines are given to people in nursing homes," explains Ellenberg. Unfortunately, this population has a relatively high death rate anyway, so it's almost impossible to say whether a given death is associated with the vaccine, she says.

As inevitable as some of those deaths, as well as other adverse events, may be, FDA remains vigilant in its efforts to improve vaccine safety. The agency will continue to be aggressive, says Hardegree, in its efforts, along with manufacturers and other government agencies, to get safer vaccines on the market.

Assessing Risks with Polio Vaccines

In 1955, the year the polio vaccine was licensed, an individual lot of that vaccine infected 60 people directly and 89 who came in contact with them because the manufacturer had failed to totally inactivate the virus. But, as awful as that was, parents of other children weren't deterred from having their children vaccinated.

"When a disease is rampant, the public will accept high-risk products," says Jerome A. Donlon, M.D., Ph.D., director of CBER's Office of Establishment Licensing and Product Surveillance.

There have been no reported cases of paralysis caused by naturally occurring polio virus in the United States since 1979. However, according to the national Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices, about six to eight people get polio from the live vaccine each year.

Unlike the vaccine-associated cases in 1955, these modern cases are not caused by manufacturing failures. Instead, most of the cases are in people with previously undetected immune deficiencies.

The problem is that the virus, though weakened, is still active. The committee is developing a new polio vaccination policy that will include a greatly enhanced role for inactivated (killed) polio vaccine.

Developing New Pertussis Vaccines

Recent results of pertussis (whooping cough) vaccine clinical trials show that three experimental vaccines are highly effective in infants.

The trials were sponsored by the National Institute of Allergy and Infectious Disease, part of the National Institutes of Health, in Bethesda, Md., and conducted in Italy and Sweden. The results also showed that the experimental vaccines caused fewer side effects than a vaccine currently used in the United States.

Scientists in FDA's Center for Biologics Evaluation and Research have been instrumental in developing and evaluating acellular vaccines, such as those tested in Italy and Sweden, and have collaborated with NIAID and the vaccine manufacturers to design the European trials.

Acellular vaccines contain only the parts of the pertussis bacterium thought to be important for immunity. U.S. vaccines licensed for use in infants are called whole-cell vaccines, because they contain the whole, inactivated pertussis organism.

Seizures were reported rarely in the trials, but no more frequently in any of the pertussis vaccine groups than in the control group. Side effects, such as redness, pain and swelling at the site of the injection, fever, and protracted crying, were reported less commonly with the acellular vaccines than with the whole-cell one.

FDA has made special efforts to encourage manufacturers to submit applications for the use of acellular pertussis vaccines in infants. The agency will target such applications for complete review within six months of receiving them. However, actual times to any licensing can vary, depending on the quality and completeness of the data submitted.

FDA recommends that parents continue to have their children vaccinated against pertussis with available vaccines.

About the Author

The Department of Health & Human Services is the United States government's principal agency for protecting the health of all Americans and providing essential human services, especially for those who are least able to help themselves. The department includes more than 300 programs, covering a wide spectrum of activities.