Yellow fever vaccine: An updated assessment of advanced age as a risk factor for serious adverse events

Abstract

Chen, Robert T.; and Cetron, Martin S., "Yellow fever vaccine: An updated assessment of advanced age as a risk factor for serious adverse events" (2005 AbstractSince 1996, the scientific community has become aware of 14 reports of yellow fever vaccine (YEL)-associated viscerotropic disease (YEL-AVD) cases and four reports of YEL-associated neurotropic disease (YEL-AND) worldwide, changing our understanding of the risks of the vaccine. Based on 722 adverse event reports after YEL submitted to the U.S. Vaccine Adverse Event Reporting System in 1990-2002, we updated the estimates of the age-adjusted reporting rates of serious adverse events, YEL-AVD and YEL-AND. We found that the reporting rates of serious adverse events were significantly higher among vaccinees aged ≥60 years than among those 19-29 years of age (reporting rate ratio = 5.9, 95% CI 1.6-22.2). Yellow fever is a serious and potentially fatal disease. For elderly travelers, the risk for severe illness and death due to yellow fever infection should be balanced against the risk of a serious adverse event due to YEL.

A Randomized, Double-Blind, Controlled Trial of the 17D Yellow Fever Virus Vaccine Given in Combination with Immune Globulin or Placebo: Comparative Viremia and Immunogenicity

“…9,10 Advanced age, thymus disease, and other immunosuppressive conditions are major risk factors associated with YF-AVD. 3,[11][12][13] One explanation for the increased reports of vaccineassociated adverse events is increased surveillance and reporting. Interestingly, before the approval of hepatitis A vaccine in 1996, the YF vaccine was commonly given simultaneously with Ig (for hepatitis A prophylaxis) during pretravel immunizations.…”

Incidence of Yellow Fever Vaccine-Associated Neurotropic Disease

“…Only patients with serious neurologic adverse events were included, i.e., adverse events that resulted in life-threatening illness, inpatient hospitalization, persistent or significant disability, or death. 15 Data were extracted from medical charts, including demographic variables, past medical story, indication for YF vaccination, concomitant vaccinations, interval between YF vaccination and first symptoms, diagnostic workup, and outcome.…”

“…11 Likewise, naturally acquired YF is also more likely to be severe among males. 17 Although YF-AND has been the most common serious adverse event associated with YF vaccination, its incidence has been constantly estimated as low, between 0.4 and 0.8 cases per 100,000 doses in the United States, 4,11,15 and in Europe. 16 Of the 23 encephalitis cases reported during 1945-2002 worldwide among > 200 million doses, 16 cases (69.6%) have been reported in newborns and infants < 9 months of age, 18 which suggests that the incidence of post-vaccinal encephalitis is much lower when contraindications for YF vaccine administration are followed, i.e., absolute contraindication for newborns and infants < 6 months of age, and limited use between 6 and 9 months of age (only if risk of disease is significant and other methods of prevention cannot be used).…”

“…This finding is in part related to inclusion of acute meningitis in our study because no cases of acute meningitis were reported in most previous studies. However, meningitis is not trivial and would qualify for a serious adverse event according to most classifications, 15 such as the one used in our study, in which adverse events were rated serious if they led to inpatient hospitalization. Including these manifestations in the definition of YF-AND would greatly enhance its estimated incidence, which may come closer to the average risk of YF disease for an non-immunized traveler in South America and sub-Saharan Africa, which is estimated to be 10 and 100 per 100,000 travelers per month, respectively.…”

Safety and tolerability of yellow fever vaccines

“…12 All AEFI are monitored by a passive surveillance system known as the Vaccine Adverse Event Reporting System, operated by CDC and the US Food and Drug Administration (FDA). 13 AEFI, following yellow fever vaccination, are typically mild and nonspecific. 14 Interestingly, studies have suggested that there is a higher incidence of local inflammatory events in female vaccine recipients, than in males.…”