High-Dose Flu Vaccine Deemed Safe in Elderly

Developing more effective influenza vaccines for the elderly, who are often hit hardest when infected, has been a research focus for decades.

A 2014 study in adults aged older than 65 years showed that progress is being made. Its results indicated that a high-dose inactivated influenza vaccine (IIV-HD) was 24.2% more effective than a standard-dose inactivated influenza vaccine (IIV-SD).

Using the same study participants, the original investigators looked for serious adverse events (SAEs) and potential sequelae or complications of influenza infection. Published ahead-of-print in the journal Vaccine, this new study suggests that IIV-HD reduces the risk of influenza-related SAEs.

Using the original double-blind, randomized, active-controlled, multicenter trial, the researchers followed participants for 6 to 8 months post-vaccination, tracking the occurrence of influenza and SAEs.

In this subsequent study, 2 physicians blinded to the treatment group independently reviewed all SAE diagnostic categories that were reported during the 2 years after immunization. They classified SAEs as possibly related to influenza, and a third physician reviewed the SAEs on which the pair could not agree.

Among the 31,989 participants, 15,991 were immunized with IIV-HD and 15,998 received IIV-SD. Patients who received IIV-HD were significantly less likely to experience SAEs than those immunized with IIV-SD.

The high-dose formulation was also significantly better at preventing serious cardio-respiratory events, especially pneumonia possibly related to influenza, than the standard-dose formulation.

The high-dose formulation was also more effective at preventing all-cause hospitalizations compared with the standard-dose formulation, but this result was marginally significant.

Some study findings, particularly those related to asthma and chronic obstructive pulmonary disease, were widely disparate from year to year. The researchers credited these large differences to the 2 influenza season’s epidemiology and the flu’s role in triggering new onset or exacerbations of bronchial events and any hospitalization. They also noted that unlike the original study, this study did not require laboratory confirmation of influenza.