A high-dose influenza vaccine not only boosted immune response in older adults, it also protected against actual illness better than traditional flu shots, according to a long-awaited study published Wednesday.
The jab that contains four times as much antigen as the regular vaccine was about 24 percent more effective in preventing lab-confirmed flu, a potential boon to people aged 65 and older. Seniors don’t respond well to traditional flu vaccines and account for two-thirds of hospitalizations and 90 percent of deaths caused by the seasonal viruses.
“That’s the whole basis of why we developed that vaccine,” said Dr. David Greenberg, vice president of scientific and medical affairs and chief medical officer for Sanofi Pasteur, the firm that makes regular Fluzone and its cousin, Fluzone High-Dose.
The drug maker had previously released top-line data from the study to a vaccine advisory committee of the Centers for Disease Control and Prevention. But Wednesday’s publication of full data in The New England Journal of Medicine will allow researchers and others to take a closer look, said Dr. Betz Halloran, a vaccine-trial expert in Fred Hutchinson Cancer Research Center’s Public Health Sciences Division.
“I have no doubt the study was well-conducted,” she said, adding later: “Since the public health burden is high among older adults, the 24 percent improvement would be an important public health benefit.”
Sanofi researchers studied results from nearly 32,000 participants enrolled at 126 research centers in the U.S. and Canada during two flu seasons: the relatively mild 2011-2012 season and the moderately severe 2012-2013 season.
About half of the participants in the randomized, controlled trial received doses of regular Fluzone, a vaccine that protects against three strains of flu with 15 micrograms per strain of the antigen, which stimulates the immune system. The other half received the high-dose version of Fluzone, first approved in 2009, which contains 60 micrograms of antigen per strain in each shot.
Dr. Mike Jackson, an assistant scientific investigator at the Group Health Research Institute in Seattle and a Fred Hutch collaborator, said the study showed that the high-dose vaccine was particularly effective against the H3N2 flu strain.
“It’s pretty encouraging,” he said, noting that in flu seasons dominated by H3N2 the vaccine is less effective among seniors.
That’s because as people age, their immune systems weaken, becoming less able to mount a robust response to new infections – or to vaccines that mimic the infections.
Still, it’s important to note that flu vaccines are not perfect – and the high-dose Fluzone is no exception. Flu shots were effective in about 61 percent of adults and children during last year’s flu season, according to the CDC. But the vaccine is typically effective in only about half of older adults; with the high-dose Fluzone, the efficacy among seniors would rise to about 62 percent, the researchers said.
At the CDC, infectious disease expert Dr. Lisa Grohskopf said officials have been waiting for the new results, which look promising. But the agency has not recommended that older adults get the high-dose vaccine rather than the traditional shot. The findings still need to be formally considered, she added.
About 8 million doses of high-dose Fluzone were distributed during the last flu season, which meant that about one in four older adults got the boosted dose, Greenberg said. He wouldn’t say how many doses were set for delivery this flu season, in which manufacturers expect to produce between 153 million and 158 million shots, but he said there would be enough to go around.
“I think you can give the message that it will be readily available,” he said.
High-dose Fluzone could be a boon for Sanofi as well. The list price is $28.65 per dose, which compares to a list price of $9.94 to $20.34 for other Fluzone vaccines, a spokesman said. The vaccine is covered through the federal Medicare and Medicaid programs, so for people aged 65 and older, there’s no co-payment required.
Older adults who can’t find the high-dose drug shouldn’t skip vaccination searching for it, said Dr. William Schaffner, a professor of preventive medicine at Vanderbilt University. Numbers vary widely, but flu causes an average of nearly 24,000 deaths and more than 200,000 hospitalizations per year, according to the CDC.
Also, don’t worry if the high-dose vaccine boosts some low-key side effects as well. Schaffner said his own arm was a little sore after last year’s shot.
“It’s got more punch,” he said, “but it’s important to be protected.”
JoNel Aleccia is a former staff writer at Fred Hutchinson Cancer Research Center. From 2008 to 2014, she was a national health reporter for NBC News and msnbc.com. Prior to that she was a reporter, editor and columnist for more than two decades at newspapers in the Northwest.