Health experts are worried about whether coronavirus vaccines under development will adequately protect the elderly, sparking efforts to make sure there are shots that can help the vulnerable group.
Older adults are especially susceptible to infection by the virus, and at higher risk of falling critically ill and dying, at least partly because their immune systems have lost strength with age. Public-health officials and scientists are concerned that a weakened immune system could also limit the effectiveness of a coronavirus vaccine, just as it has sapped the power of other shots in older people.
“It would not be particularly encouraging if we have a vaccine that’s capable of protecting 20-year-olds who probably have a pretty low risk anyway of getting sick, and doesn’t work at all for people over 65,” Francis Collins, director of the National Institutes of Health, said in an interview.
To find a vaccine that works safely in older adults, researchers at Pfizer PFE -1.14% Inc. and other companies are exploring possible options such as increasing the doses or adding a booster to the shot. At least one vaccine specifically for the elderly is in development. And Pfizer, the University of Oxford and others have started testing their coronavirus vaccine candidates in older adults.
Some of the experimental vaccines “may turn out to be better for older individuals, and that’ll be a big issue in terms of how we then end up deploying these,” Dr. Collins said.
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Older adults have been especially hard hit by the new coronavirus. Between March and mid-June, Americans over the age of 65 had the highest rate of hospitalization among all age groups, about double the rate for people 50 to 64 years old and five times the rate for 18- to 49-year-olds, according to the Centers for Disease Control and Prevention.
Vaccines will be crucial, public-health experts say, to stopping the spread of the virus. More than 100 are in development and more than a dozen are in human testing, according to the World Health Organization.
The shots work by tricking the body into thinking it has been infected with a virus, prompting the immune system to make antibodies to fight the pathogen. Yet antibody production weakens over time, part of a process known as immunosenescence. Researchers aren’t sure why, aside from the fact that the body generally weakens with age.
The loss of immune system strength makes older adults more susceptible to bacterial and viral infections such as influenza. Some 90% of flu deaths in the U.S. each year are of people over the age of 65.
And flu vaccines tend not to protect older adults as well as they defend younger people. Research shows the vaccines protect between 70% and 90% of children and younger adults, but 30% to 50% of adults over 65.
“We’re just starting to understand some of the ways to overcome those immune responses,” said Dr. Kawsar Talaat, deputy director of clinical research for the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health, who is slated to help coronavirus vaccine developers test their shots in older adults. “We hadn’t been designing vaccines for the elderly for a long time.”
The Food and Drug Administration is working with companies to make it easier for experimental vaccines to be tested in older adults earlier during clinical trials, and alongside younger subjects, an agency spokesman said. Moderna Inc. MRNA -4.70% is among the companies already testing its experimental shot in adults older than 55, while Johnson & Johnson JNJ -1.18% plans to after it begins testing next month.
Pfizer, which is also testing its potential coronavirus vaccines in older people, is studying whether increasing the dosage could protect the elderly better. Higher doses have helped make flu vaccines more effective in the elderly.
Researchers at the New York drugmaker are also curious whether their gene-based technology might prove more effective in elderly people than shots based on older, different technologies, said Kathrin Jansen, Pfizer’s head of vaccine research and development.
The unproven technology uses messenger RNA, or mRNA, programmed to tell cells to make proteins that can protect against the coronavirus. Pfizer wants to see whether the synthesized mRNA spurs both a broad immune response, which may not be as strong in older adults, as well as a targeted response that makes up for the gap, Dr. Jansen said.
The more powerful punch could “help overcome the difference between younger adults’ responses and that of an older adult,” Dr. Jansen said in an interview.
Some companies are considering the use of a booster, or adjuvant, to strengthen a vaccine’s effect on the immune systems of older adults. An adjuvant in Shingrix, a shingles vaccine from GlaxoSmithKline GSK -0.02% PLC, helps the shot safely reduce the risk of contracting the disease by more than 90% in older people, almost twice the percentage of the other shingles vaccine in the U.S., according to the CDC.
Glaxo provided one of its adjuvants to Sanofi SA SNY +0.25% and six other drugmakers working on coronavirus vaccines, said Dr. Thomas Breuer, chief medical officer of GSK vaccines. Glaxo had used that adjuvant in an H1N1 vaccine.
Meantime, researchers at Boston Children’s Hospital are trying to develop a vaccine specifically for older adults. The researchers are screening vaccine candidates against white blood cells donated by older people to see whether any of the shots would work better in the elderly, said Ofer Levy, director of the hospital’s vaccines program.
The hospital researchers have narrowed the search to about seven different vaccine candidates, and are also evaluating about 50 potential adjuvants that could be added, Dr. Levy said. They hope to begin testing a vaccine in people ages 65 and older next year, he said.
Write to Jared S. Hopkins at [email protected]