High-dose flu vaccine reducing hospitalizations in seniors, study shows

PORTLAND, Ore.—High-dose influenza vaccine reduces hospitalization for the virus among Oregon seniors, a new Oregon Health Authority study has found.

 

The study of more than 144,000 seniors, ages 65 and older, living in the Portland metropolitan area showed that high-dose flu vaccine was 31 percent more effective at preventing senior flu-related hospitalizations than the standard-dose flu vaccine during the 2016-2017 season, according to the study appearing in the scientific journal Vaccine.

 

A high-dose vaccine contains four times the antigen of a standard flu vaccine. Antigens are the molecular structures on the surfaces of viruses that trigger the body’s immune response. Seniors typically have a weaker immune response to standard influenza vaccines than younger adults, and benefit from vaccines that are high-dose or "adjuvanted" specifically for seniors.

 

Putting another chemical, an adjuvant, into the vaccine helps create a stronger reaction to the antigen of the vaccine. Seniors should get a vaccine that is intended to boost their immune response.

 

Steve Robison, epidemiologist in the Oregon Immunization Program, is the lead study author. Co-author is Anne Thomas, M.D., public health physician in the Acute and Communicable Disease Prevention Section. They say protecting vulnerable seniors during flu season each year is a constant challenge.

 

"Seniors are at greater risk of severe illness from flu," Thomas said. "What’s more, typical flu vaccine doses aren’t adequately protective for many seniors. We wanted to know whether a widely used high-dose flu vaccine would benefit a large population of seniors, particularly in reducing hospitalizations."

 

For their study, Robison and Thomas focused on seniors who reported receiving a flu vaccine by Dec. 11, 2016, which is roughly four weeks before the typical onset of substantial local flu disease activity. It also ensured that seniors who received the vaccine had enough time to achieve full "seroconversion," which is when flu antibodies develop and become detectable.

 

The study population consisted of 78,602 seniors who received high-dose flu vaccine and 65,705 seniors who received the standard vaccine dose.

 

Robison and Thomas found that senior use of high-dose flu vaccine, compared with standard-dose vaccine, was associated with a "substantial reduction in the risk of hospitalization" with laboratory-confirmed influenza.

 

"The message is: do not give the standard flu vaccine to seniors. Give the high-dose vaccine or adjuvanted vaccine," Robison said. He said that while the adjuvanted vaccine was not addressed in the study, it also is a good alternative to the standard-dose vaccine for seniors.

 

Robison explained that because adult influenza is not a reportable disease in the United States, only limited data on actual amounts of disease exist. However, due to funding from CDC’s Emerging Infections Program, the OHA’s Acute and Communicable Disease Prevention program tracks influenza hospitalizations in the Portland metro area.

 

"We are fortunate here in Oregon to have accurate data on flu hospitalizations," Robison said. "Coupled with a strong immunization registry in our state, we have the ability to use our hospitalization and vaccination data to figure out how well vaccines are working. In this case, our study tells us at least one of these vaccines may be working better than we think."

 

The study is available on the Science Direct website.