Increasing the vaccine dosage is a proven method to improve vaccine efficacy in older people
A more effective flu vaccine for older patients may be available in Australia from next year.
Sanofi Pasteur’s high-dose trivalent influenza vaccine, Fluzone, has long been used in the US and Canada, after gaining FDA approval in 2009.
The company hopes to launch the vaccine in the Australian market in 2018.
Speaking at the Adult Immunisation Forum in Melbourne last month, Christian Felter, Sanofi Pasteur Australia’s head of medical, said the high-dose vaccine was one solution to the issue of immunosenescence in older people.
The immune system starts to fail predictably after the age of 50, raising the risk of infection and lowering the effectiveness of vaccines.
The current quadrivalent influenza vaccine, available for free to older adults in Australia, has an efficacy of only 27 to 40% in people aged 65 years or older.
Every year, influenza kills around 3,000 older patients in Australia, despite influenza vaccine coverage rates of around 75%.
New generation vaccines, such as Fluzone, could really make a difference, Mr Felter said.
In 2014, the company published its pivotal RCT on Fluzone, involving around 32,000 participants of mean age 73.1
The study showed a relative improved efficacy of 24.3% for the high-dose vaccine against the standard dose trivalent vaccine.
The modest increase in costs from funding the high-dose vaccine was more than compensated for by reduced hospitalisations, Mr Felter said.
Further analysis found no significant evidence that baseline age, comorbidity, or frailty modified the efficacy of the high-dose vaccine.2
The high-dose formula, given as a single 0.5mL intramuscular injection, contains four times the amount of hemagglutinin in the standard dose. It provides protection against three strains, two A lineages (H3N2 and H1N1) and one B lineage.
Around 70 million doses had been distributed since being licensed eight years ago and no safety concerns had been identified in that time, Mr Felter said.
“When we are able to bring this vaccine to Australia, hopefully next year, you are going to have infinitely more information about the product that they did in the US when they launched it,” he said.
An FDA-funded retrospective cohort study of around 10 million people revealed that the high-dose vaccine was significantly more effective at reducing influenza-related hospital admissions.3
But a more recent study, funded by FDA and CDC, found that the high-dose vaccine did not outperform the standard-dose vaccine in the 2013-2014 season, although it did in the 2012-2013 season, reducing influenza deaths by around 35%.4
“There are several plausible reasons,” the study authors said. These could include differences in the circulation patterns of specific influenza viruses by season, and differences in the antigenic-relatedness of vaccine and wild-type viruses by season.
Raising the vaccine dosage is one method to improve vaccine efficacy in older people, but there are many other strategies, including conjugation, adjuvants, and different routes of administration.
“We need research to improve vaccine immunogenicity in the elderly,” said epidemiologist Professor Raina MacIntyre, the head of the School of Public Health and Community Medicine at UNSW.
“It is possible if we invest in the technology, invest in the research and development, that we can come up with solutions to immunosenescence.
“We shouldn’t just assume that frail older people can’t respond to vaccines. We need to try harder to find these solutions.”
References:
1 N Engl J Med. 2014 Aug 14;371(7):635-45.
2 Vaccine. 2015 Aug 26;33(36):4565-71
