strongly or however weakly—that a vaccine is associated with an adverse event, one asks, “Does this make sense given what is known and generally accepted about the biological response to the natural infection, to the vaccine, and what is known about the pathophysiology of the adverse health outcome?”
As described in Chapter 1, the committee was tasked to assess the relationship between a specific adverse health outcome and a specific vaccine. A professional medical librarian conducted three waves of comprehensive literature searches of the published, peer-reviewed biomedical literature using MEDLINE (1950–present); EMBASE (1980–present); BIOSIS (1969– 2005); Web of Science, consisting of the Science Citation Index (1900–present) and the Social Science Citation Index (1956–present); and search terms specific to each vaccine–adverse event relationship under study. Appendix C contains the search strategies used. The first wave of searches included the earliest date of the database to the date of the first search. Follow-up searches were conducted in August 2010 and late December 2010 to ensure that articles published after the initial search were not missed. On occasion, specialized searches were conducted to supplement the general searches. Also, review of the reference list of an article sometimes revealed studies not captured by the general search. These studies were retrieved.
Titles and abstracts, where available, were reviewed to screen out articles that did not address one of the potential vaccine adverse events to be reviewed or that were not primary research articles. See Figure 2-1. For example, the committee did not assess review articles. The committee restricted its review to those vaccines used in the United States, even if the study was conducted outside of the United States, with a few exceptions that will be discussed in the vaccine-specific chapters that follow. Articles were retrieved and reviewed again for relevance to the committee charge. Articles written in languages other than English were translated using Google Translate or a professional translation service. The committee did not include in its reviews data presented only in abstract form or in otherwise unpublished formats, with one exception described in Chapter 9, “Human Papillomavirus Vaccine.” An individual report from the Vaccine Adverse Event Reporting System was reviewed only if it had been described in a peer-reviewed research study and the committee wanted additional information. Decisions from the Vaccine Injury Compensation Program were not reviewed, because they are not published in the peer-reviewed medical literature. The committee did not review the conclusions contained in earlier IOM reports. The committee reviewed the data and made conclusions independently.