While vaccinations remain one of the most potent weapons we have against infectious disease, they don't work as well as our immune systems age. Scientists are conducting experiments to understand why vaccines are less effective in older adults, and what can be done to make them more effective.

Influenza takes its heaviest toll among those with weakened immune systems, including the old. Scientists at the Mayo Clinic in Rochester, Minnesota, published the results of studies done on influenza vaccine in older adults in the December 2001 issue of the Journal of Virology. They monitored 153 residents of a retirement community, aged 65 to 98 years, who had received influenza vaccine. The vaccine was trivalent, containing elements of three different flu strains. At 28 days, the scientists found that only 17% of the persons vaccinated were immune to all 3 strains. 46% were found to have no immunity to any of the three strains. The likelihood of the subjects responding to the vaccine was found to decline with age.

Some vaccines contain adjuvants, compounds that boost the immune response to the antigens in the vaccines. Italian scientists reported in the European Journal of Epidemiology that an influenza vaccine with an adjuvant could boost the immune response of older adults. About 200 people over the age of 65 were given a flu vaccination with adjuvant and compared to 100 who had received the more conventional flu vaccine. The adjuvant vaccine was found to significantly boost the immune responses of the older adults who had received it, as compared to those who had received the conventional form. There were no significant adverse effects from the adjuvant form of the vaccine, suggesting that this method may be of real benefit.

Scientists at the University of Minnesota School of Medicine have recently commented on the efficacy of the pneumococcal vaccine in the older population. They note that the vaccine has been found to be 56 to 81% effective in preventing pneumonia from the bacterium Pneumococcus, and that it has proven benefit in reducing the risk of community-acquired pneumonia among older adults when it is given in conjunction with influenza vaccines. They suggest further research to identify those older adults less likely to respond well to the vaccine, and development of more potent forms of the vaccine to be used for these at-risk individuals.

With improved health in general, more older adults are traveling to more exotic destinations. Such individuals, like their younger counterparts, need to investigate what infectious diseases are endemic to their destinations, and obtain the necessary vaccines prior to traveling. Scientists at the Beth Israel Deaconess Medical Center in Boston reviewed the known efficacy of such vaccines in older adults in an article in the November 2001 issue of Clinical Infectious Diseases. They note that few studies have looked exclusively at the efficacy of travel-related vaccines in older populations, but it is known that older adults do not mount as strong an immune response to vaccines against hepatitis A and rabies. They recommend more extensive inquiry into the use of these vaccines in older adults.