Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices—United States, 2018–19 Influenza Season

As compared with a standard-dose vaccine, a high-dose, trivalent, inactivated influenza vaccine (IIV3-HD) improves antibody responses to influenza among adults 65 years of age or older. This study evaluated whether IIV3-HD also improves protection against laboratory-confirmed influenza illness.

Influenza-associated morbidity and mortality has not decreased in the last decade, despite increased receipt of vaccine. To improve the immunogenicity of influenza vaccine, a high-dose (HD) trivalent, inactivated influenza vaccine was developed. A multicenter, randomized, double-blind controlled study was conducted to compare HD vaccine (which contains 60 microg of hemagglutinin per strain) with the licensed standard-dose (SD) vaccine (which contains 15 microg of hemagglutinin per strain) in adults > or = 65 years of age. HD vaccine was administered to 2575 subjects, and SD vaccine was administered to 1262 subjects. There was a statistically significant increase in the rates of seroconversion and mean hemagglutination inhibition titers at day 28 after vaccination among those who received HD vaccine, compared with those who received SD vaccine. Mean postvaccination titers for individuals who received HD vaccine were 116 for H1N1, 609 for H3N2, and 69 for B strain; for those who received SD vaccine, mean postvaccination titers were as 67 for H1N1, 333 for H3N2, and 52 for B strain. The HD vaccine met superiority criteria for both A strains, and the responses for B strain met non-inferiority criteria. Seroprotection rates were also higher for those who received HD vaccine than for those who received SD vaccine vaccine, for all strains. Local reactions were more frequent in individuals who received HD vaccine, but the reactions were mild to moderate. There was a statistically significant increase in the level of antibody response induced by HD influenza vaccine, compared with that induced by SD vaccine, without an attendant increase in the rate or severity of clinically relevant adverse reactions. These results suggest that the high-dose vaccine may provide improved protective benefits for older adults. ClinicalTrials.gov identifier: NCT00391053 .

We estimated influenza- and respiratory syncytial virus (RSV)-associated hospitalizations by age, high-risk status and outcome, during the 1996/1997-1999/2000 respiratory seasons among adults who did not receive influenza vaccine. Using three health maintenance organization (HMO) databases and local viral surveillance data, we identified weeks when influenza and RSV were circulating and estimated influenza- and RSV-associated hospitalizations. Persons aged > or = 65 years with and without high-risk conditions had significantly increased rates of influenza-associated hospitalizations for pneumonia and influenza, and circulatory and respiratory diseases. Persons aged > or = 65 years with high-risk conditions also had significantly increased rates of influenza-associated hospitalizations for cardiac conditions (16.9 per 10,000 person periods). Relative to the influenza estimates for high-risk persons > or = 65 years, we found lower rates of RSV-associated hospitalizations for pneumonia and influenza diseases (23.4 per 10,000 person periods), cardiac diseases (4.3 per 10,000 person periods) and circulatory and respiratory diseases (44.0 per 10,000 person periods). Among low-risk persons aged 50-64 years, we did not identify significantly elevated rates of influenza- or RSV-associated hospitalizations. Excess hospitalization estimates among adults aged > or = 65 years and high-risk 50-64 year olds during the influenza season suggest that these groups should have priority for influenza vaccine during vaccine shortages.