COVID-19 vaccine efficacy waning, but still worth getting, experts say

  • Jacqueline Coll gives the COVID-19 vaccine to Donna Infante as part of the first round of vaccinations for frontline health care workers at Monadnock Community Hospital Friday. Staff photo by Ben Conant

For the Keene Sentinel
Published: 7/26/2022 3:16:07 PM

For many people, the word vaccine is synonymous with immunity. While the flu shot has a lower efficacy against infection, people vaccinated against diseases like polio or measles can get exposed to those viruses and be fairly certain they won’t get sick.

So when a vaccine was developed for COVID-19, many people hurried to get it, and hurried back for a booster when they became available. But some of them have become skeptical about the shot in recent months as more and more vaccinated people report infections, sometimes repeatedly.

Dr. Aalok Khole, an infectious disease expert at Cheshire Medical Center in Keene, said the omicron BA.5 variant has now become the dominant strain of COVID-19 across the nation as well as the U.S. Department of Health and Human Services’ District 1, which covers New England. Khole said this strain appears to be more transmissible and more resistant to inoculation.

“BA.4 and BA.5, the existing dominant strains, have the ability to evade immunity derived from both infection and vaccines,” Khole explained. “This is making reinfections more likely, even within a few weeks of their last infection, which might have been from a different, then dominant, strain.”

Because the vaccines currently on the market were developed based on the biology of the original COVID-19 strains, they are becoming less effective against newer mutations of the virus, according to Khole and other regional and national infectious disease experts. This has left some wondering if it’s worth the bother to keep up on their booster shots or get vaccinated in the first place.

Dr. Joseph Siedner, an infectious disease specialist at Massachusetts General Hospital in Boston, says getting vaccinated and boosted is indeed still worth it. While he acknowledged that available vaccines aren’t quite as effective against newer variants, they still go a long way toward keeping patients alive and out of the ICU.

“Although the vaccines also protected against mild infection with newer variants, that no longer seems to be the case, and certainly not to the same extent,” Siedner said. “But if the choice is between getting a vaccine and getting a mild infection or not getting one and ending up in the hospital or worse, the case for vaccination is still quite clear.”

Khole and Siedner both said COVID-19 is likely to become endemic, which means the virus will consistently remain in communities, but will be manageable, much like the common flu. Also similarly to the flu, the doctors said COVID-19 is expected to continuously mutate, meaning that new vaccines will always be in the works to keep up with the latest strains.

Dr. Joseph Ebner, chief medical officer at Speare Memorial Hospital in Plymouth, has said patients should not be discouraged by the waning efficacy of existing COVID-19 vaccines. He said that while it’s true that vaccines will likely be more effective against current variants in the future, getting one now is still better than having no protection at all.

“All viruses have some mutation over time,” he said, “but the vaccines and boosters are likely to remain somewhat effective even as the virus mutates.”

According to Dr. William Schaffner, a professor of medicine in the Division of Infectious Diseases at Vanderbilt University in Tennessee, there’s another reason why vaccines for respiratory infections, like the flu or COVID-19, don’t offer full immunity the way some other vaccines do. He said this has to do with how viruses move throughout the body.

In the case of polio, Schaffner explained, the virus does its damage — and causes its worst symptoms — in the spinal cord. But to get there, it must travel from its point of entry and through the bloodstream, where the antibodies of a vaccinated person would destroy the virus before it makes it to the spinal cord.

But with respiratory illnesses, a virus doesn’t have to go through the bloodstream before causing symptoms in the respiratory tract, so antibodies don’t get a chance to do their job before an infected person starts to experience those cold-like symptoms.

“It doesn’t have to travel to give me a minor infection,” Schaffner said. “What the antibodies do is, when that COVID virus gets out of the respiratory tract and starts to go to other organs, that’s when the protection logs in.”

It’s when COVID-19 travels beyond the respiratory system that the disease becomes especially dangerous, he noted. So even though COVID-19 vaccines may never completely prevent people from feeling sick because of the virus, they can prevent it from infecting other organs, thereby minimizing the chance of severe illness.

Each of the doctors also noted there is some additional protection to be gained from natural immunity after recovering from a COVID-19 infection. While some said more research is needed to know the full extent of that protection, it is clear that any immunity from getting sick tends to wane over time, just as the vaccines themselves do.

“It turns out that a combination of infection and vaccination seems to give the immune system the greatest boost,” Siedner said, “so having both can be particularly helpful in preventing future infections.”

Schaffner agreed and said it’s something of a medical uncertainty why natural immunity to some viruses, like measles, lasts a lifetime, while that’s not the case for other illnesses. “It’s not something we completely understand,” he said.

He sympathized with those who doubt the vaccines due to their diminishing protection in the face of new strains of COVID-19. But he said he always emphasizes that the science behind the ongoing need for new vaccines and continuous booster shots is much like the science behind the flu: New mutations require updated protection.

According to the Centers for Disease Control and Prevention, flu vaccines are reviewed annually and updated as needed. The CDC says while many strains of the flu are transmitted throughout communities each year, vaccines are designed to protect against the four strains researchers predict will be most common in the coming season.

Khole also said he understands the frustration that people are feeling. He said those who want to feel further protected can still do so by masking indoors, social distancing, practicing good hand hygiene and following other established guidelines when case counts in their communities are on the rise.

“It is crucial to understand that with the extent of home testing, numbers are likely grossly underreported — so better to be safe than sorry,” Khole said.

These articles are being shared by partners in The Granite State News Collaborative. For more information visit 

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