This is one of a series of articles in which reporters from WHYY’s Health Desk Help Desk answer questions about vaccines and COVID-19 submitted by you, our audience.
Pharmaceutical companies that produce COVID-19 vaccines have been quick to announce that people will likely need a booster shot to maintain their immune response to the virus and its variants.
Pfizer Chief Executive Albert Bourla has said people will “likely” need one every 12 months, similar to an annual flu shot. Meanwhile, Moderna CEO Stephane Bancel wants to produce a vaccine targeting the variant of COVID-19 first detected in South Africa, and expects regular boosters will be needed. Clinical trials for that are already underway.
However, scientists argue it’s too soon to know whether or not people will need boosters. That all depends on how long the vaccines maintain a person’s immune response, and how effective they are against multiple variants of the virus.
Here’s what we know so far.
What are booster shots used for?
A regular vaccine is designed to protect people from infectious agents. However, a person’s immunity can slowly dissipate over time. So, once in a while, you might need a booster shot to provoke a stronger immune response that can protect you.
Another reason for booster shots is when an infectious agent changes, as with the flu. People need annual flu shots because it’s a different virus from time to time.
How long will we be protected from COVID-19 with the current vaccines?
Scientists don’t have all the answers yet.
Pfizer and Moderna studies of their own vaccines show the shot remains effective for at least six months. But more research is needed to know if it works longer than that.
“The protection is very robust, it does decline slowly, but you still have memory response, so the protection lasts a long time, though it does go off slightly over time,” said Dr. Frederic Bushman, chair of the University of Pennsylvania’s microbiology department.
The other key factor is whether or not the virus is changing. Bushman said there is proof of that. His team conducts weekly reporting on viral whole genome sequencing, and they are seeing new variants appearing in our region.
“The most recent batch we did, samples from the last few weeks, almost all the sequences were variants — the UK derived variant, the Brazil derived variant, the South Africa derived variant, and others,” Bushman said. “So the virus is evolving to spread more efficiently in humans, and that’s accompanied by changes in the viral proteins, the surface spike protein. So, the question is, ‘Will we need a different vaccine to block infection with new variants as they arise?’”
Research has shown the Pfizer and Moderna vaccines work against some of the variants, and more studies are being conducted.
How can researchers get more answers?
Bushman said scientists can take antibodies from the blood of someone who has been vaccinated against COVID-19, and use it to neutralize viruses in a laboratory. These scientists can check the different variants to make sure they’re neutralized reasonably well.
Scientists also can conduct population-level surveys, Bushman said. If vaccinated people become infected, researchers can look at what viral variant they have. Viral whole genome sequencing can display what variant they have and researchers can look for patterns.
How long will it take to produce and approve boosters?
The good news is that the MrNA vaccines are very amenable to updating, Bushman said.
“You just change the nucleic acid sequence to match that of the new variant, and voilà, you’ve got the new vaccine,” he said. “So that can happen very fast on an engineering level. Then, there’s the whole testing and approval process. But testing can probably go pretty quickly, and similarly, approval. So, I think we probably could implement a new vaccine quickly. But it would be much better if we didn’t have to.”
Vaccines, mask-wearing, and physical distancing help fight against new variants, Bushman said.
“So, if we can keep those up and suppress the levels of virus, that reduces the chances of the virus mutating. If there’s a lot less virus, a lot less transmission, there will be a lot less viral evolution,” he said. “So, we have it in our power to strongly influence the situation by getting vaccinated, wearing masks, and engaging in all the precautions we’ve been hearing about.
“If we’re suppressing the virus in the U.S., but the virus is taking off in South Africa, or Brazil, or wherever, that could be an incubator for new variants that could break through the vaccines we have, so no one is safe until everyone is safe,” Bushman added. “We need to finish the job here, vaccinating and suppressing the virus, and bringing that to the rest of the world. We need to try and squelch the virus everywhere.”
The city of Philadelphia announced Tuesday that all COVID-19 restrictions, with the exception of face mask requirements, will end on June 11. In Pennsylvania, all restrictions are set to lift across the state on Memorial Day, with the exception of face mask requirements. New Jersey is lifting most of its restrictions on May 19, and Delaware on May 21.
“I can see the argument both ways. You want to reward people for getting vaccinated, you want to have something to look forward to. However, I think we really have to respond to events,” Bushman said.
“Things were looking good in India several months ago, until the virus soared because people didn’t take enough precautions, and a new variant may have contributed, and now they’re having 400,000 new infections a day. So, it can change very fast. So I think an important thing is to say, ‘We really need to keep up with precautions, we will loosen up gradually in response to data, but should things ever look to go in the wrong direction, we’re clamping down again.’”
Will there be side effects for boosters?
Moderna said in a statement that during its clinical trial of its booster, people typically reacted similarly to their second dose of the vaccines. Common side effects included pain at the injection site, fatigue, headache, as well as muscle and joint pain.
With all this talk about annual boosters, can we assume COVID-19 will act similarly to the flu?
Bushman said he’s optimistic that COVID-19 might be an easier problem to solve, because it copies its genetic material more accurately than the flu virus does.
“The genetic material comes in a lot of little pieces, and there are lots of different kinds of flus in the world. So, if two different viruses go in one cell, they can reassort all these little pieces of genome, and you can get something that has four segments from virus one or three segments from virus two, or something like that, so you can get massive changes in the sequence of the flu virus,” he said. “That doesn’t happen with SARS-COV 2 because of that reassorting — antigenic shift it’s called. So, I’m hoping SARS-COV 2 will be easier to vaccinate against.”
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