Healthy people should receive annual COVID-19 boosters to prevent widespread outbreaks, a new study from Yale University suggests.
Annual injections provide just enough frequency to prevent massive outbreaks, without undoing people.
“There seems to be a tipping point” after about a year, said senior author Jeffrey Townsend, a biostatistician and evolutionary biologist at the Yale School of Public Health. “Delaying boosting past that point quickly increases the risk of infection.”
While federal officials have suggested annual injections, this study is the first to examine the long-term results of a booster schedule and the first to show that boosters will be especially effective at intervals of no more than a year.
The study, published earlier this month, focused on people with healthy immune systems. Townsend and colleagues are embarking on a similar study of the optimal vaccination interval for people with weakened immunity from cancer treatment and other health problems.
What the study found: Annual injections prevent 75% of infections
The researchers modeled antibody levels to the virus that causes COVID-19 if someone was boosted with a Pfizer-BioNTech or Moderna vaccine every six months, one year, 18 months, two years or three years over a six-year period.
Boosting twice a year reduced infections by more than 93%, the team found, but Townsend said it’s just not realistic to ask people to get vaccinated that often.
Annual injections prevented 75% of infections, while waiting six months reduced the protection rate to just 55%. Vaccinations every three years prevented only 24% of infections, the study found.
“Delaying the administration of updated boosters has dismal consequences,” it concluded.
Boosters cannot prevent all infections
For healthy people, “an annual boost really makes a difference,” said Alex Dornburg, a bioinformatics expert at the University of North Carolina Charlotte and co-author of the study.
About 3 in 10 people become infected with COVID-19, even with an annual injection, Dornburg said. But 9 out of 10 will be infected without such updates.
Not getting a boost triples the risk of infection for six years, Yale co-author Hayley Hassley added.
The Centers for Disease Control and Prevention and most infectious disease experts encourage people of all ages to get boosters.
The booster must also continue to evolve
The virus continues to evolve, “so we have to continually develop the booster and keep it updated to the most common variant,” Hassley said.
Over time, people will lose the ability to respond effectively to the virus without boosters or reinfections, Townsend said.
The latest booster targets both the original virus and the BA.4 and BA.5. While these are no longer the most common variants, the researchers said the new booster is close enough to provide an advantage.
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Getting Vaccinated vs. become infected
The COVID-19 vaccines have side effects, making people miserable for a day or two. But an infection can be much worse, Dornburg said.
In his own case, he felt terrible for two days after his first round of injections. However, when he contracted COVID-19, his lungs ached for weeks and he was breathless climbing a single flight of stairs.
“It was horrible,” he said. “That calibrated me a little differently.”
Catching COVID-19 provides protection against future infections, but like the vaccine, this fades over time, at about the same rate, Townsend said.
And it is better not to get infected at all.
“You can’t end up in the hospital for an infection you didn’t get,” Townsend said.
In another study published Wednesday, researchers from the World Health Organization examined 26 previous articles and concluded that people who are vaccinated or infected remain better protected against serious illness a year later, compared to those who have not been vaccinated and have never been infected.
One year after being both vaccinated and infected, someone is 95% less likely to get severe COVID-19 or be hospitalized, the study found. Someone who was infected a year ago but had not been vaccinated had a 75% lower risk.
Being infected and vaccinated reduces the chance of re-infection a year later by 42%, with someone who was infected but not vaccinated having a 25% lower chance of re-infection.
When will we have better vaccines?
Unfortunately, said Dr. Eric Topol, founder and director of the Scripps Research Translational Institute, the federal government has lost its previous vaccine development momentum.
“We need durable vaccines that can work against all variants for several years,” says Topol, who was not involved in the new study. “We’re not getting the traction we need on these science projects. There’s not the will, the resources, the priority.”
That means if a worse variant emerges at some point, the US “will have to be reactive instead of having all of this up front – and that would be very sad because we know the way to get ahead of the virus and we’re not doing it,” he said.
Topol thinks nasal vaccines are needed to prevent more infections. Even if a nasal vaccine has to be given more often than injections, people won’t mind.
“I’m excited about it. I haven’t seen anything that denies it,” he said. “I would like to take a spray every few months to prevent infection.”
Please contact Karen Weintraub at kweintraub@usatoday.com.
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