Delayed Vaccination Could Increase Flu-Related Hospitalizations in Older Adults

A study in Clinical Infectious Diseases suggested older adults who delay influenza vaccinations until Oct. 1 may be at a higher risk of hospitalization, reports Healio . "Recent studies of influenza vaccine effectiveness (VE) have observed lower VE with increasing time since vaccination, suggesting that vaccine protection wanes over an influenza season," the researchers said. "These findings raise the question of optimal vaccination timing; specifically, should vaccination in late summer or early fall be avoided in favor of delaying vaccination in order to maintain greater protection during the latter part of the influenza season?" The researchers found in a typical season, delaying vaccination until October boosted flu hospitalizations if more than 14 percent of older adults usually vaccinated in August and September did not get vaccinated. The team also observed that a shift toward vaccination in August and September also raised the rate of influenza-associated hospitalizations on average, "but this result was also sensitive to influenza season timing."