As Mainers line up to get their COVID-19 shots this spring, scientists are studying whether we will have to undergo future coronavirus vaccinations. The keys to determining the need for annual shots or booster shots are how long immunity lasts and how well the vaccines perform against variants.

The answers to those questions will decide whether we will be heading to mass vaccination sites and pharmacies for COVID-19 shots in 2022, 2023 and beyond.

Will the COVID-19 shot be like an annual flu shot, or a periodic shot that you get every two, three or five years? Or will you get the COVID-19 vaccine once and not have to get it again?

The answer is a resounding “maybe.”

“The immunity likely won’t last a lifetime,” said Joshua Michaud, associate director of global health policy for the Kaiser Family Foundation, a Washington-based health policy research center. “We know there’s a robust immune response to severe infection that lasts at least nine months. Vaccine immunity does wane over time, but we don’t know how fast that will happen or to what extent it will happen.”

A vaccine study by the Veterans Administration that soon will be released shows the vaccines offer at least seven to nine months protection, and likely longer, according to the website.


Michaud said the vaccines work extremely well at preventing disease, and there’s increasing evidence the vaccines also prevent transmission of COVID-19. If there’s less transmission, the virus has fewer chances to replicate and create new variants that might reduce the effectiveness of the vaccines.

He said because scientists know the vaccines produce a strong immune response for at least nine months in real-world usage – that’s the time since the vaccines were first administered in later-stage clinical trials – that means the vaccines could maintain protection in people for much longer. But it’s not yet known how long immunity will last.

Dr. Nirav Shah, director of the Maine Center for Disease Control and Prevention, said the vaccines are a “stunning scientific success story,” but it’s still possible booster shots or annual COVID-19 shots will be needed.

“There are reasons we might see a yearly COVID shot. It’s too early to tell,” Shah said in a media briefing with reporters on Tuesday. “Cold and flu season in subsequent years might become known as COVID and flu season.”

Another possibility is a periodic booster shot, perhaps once every three to five years. Vaccine manufacturers are already researching potential booster shots.

Dr. Dora Anne Mills, chief health improvement officer for MaineHealth, the parent company of Maine Medical Center in Portland, said the booster shots could serve a dual role, to protect against variants and to boost immunity to COVID-19. Seniors may need to be prioritized for booster shots because their immune systems are weaker and immunity may wane sooner in seniors, she said.


“We know from many other vaccines that we need a boost every once in a while,” Mills said, pointing to booster shots in middle and high school for some childhood vaccinations, and for adults, a tetanus shot once every 10 years.

The booster shots will be different than for the annual flu shot – and could potentially offer protection for much longer than the flu shot – because the novel coronavirus mutates much more slowly than flu viruses, Mills said.

But the novel coronavirus does mutate.

So one of the ways to keep vaccines working well is to ramp up manufacturing of vaccines and distribute them worldwide, which helps clamp down on variants. Scientists are worried that Brazil, which is dealing with rampant infections and low vaccine supply, and is the source of one of the variants, P1, could be a source of variants for years to come.

“We have to help vaccinate the world,” Mills said. “We are not going to be safe until there is reduced transmission around the world.”

Michaud said while there’s been a lot of discussion about variants – with P1 being a particular focus because early research shows it may reduce vaccine effectiveness – the vaccines likely will still provide strong protection. The vaccines work well against other common variants, including the one from the United Kingdom and a mutation first discovered in South Africa.


He said the P1 variant and future mutations that diminish vaccine function will more likely “chip away at the edges” of vaccine effectiveness rather than completely escape the immune response vaccines create.

“It’s important to know the extent to which the variant evades immunity, and that we don’t have a real good handle on it (for P1),” Michaud said. “How much vaccine evasion is too much? That is to be determined.”

Michaud said another factor is that lab studies that examine COVID-19 antibody production to determine whether the virus is evading the vaccine do not take into account the full immune response, which is much more complicated than what can be done in a lab.

Dr. Monica Gandhi, an infectious disease expert from the University of California San Francisco, said in a March 21 tweet that promising early research shows that the body’s full immune response after vaccination is working to protect people from COVID-19. She said antibodies are only the “tip of the iceberg” in how the body responds to invading viruses.

“The public focus on (variants) detracts from realizing how amazing these vaccines are,” Gandhi said.

Michaud said one way scientists are looking at a permanent solution to COVID-19 and future variants is to create a “universal vaccine” that would work against all variants.

“The holy grail of the coronavirus vaccine, the universal vaccine, would be effective against all current variants and future variants. The universal vaccine would target parts of the coronavirus that don’t mutate very much,” Michaud said. “Some people think we can get there.”

But Michaud said while studies are underway on a universal vaccine, it may not happen.

“They have been trying to develop a universal influenza vaccine for decades, and it always seems to be another decade away from happening,” he said.

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