Researchers Predict Whether COVID Vaccines Will Protect Against Variants

With the constant rise of new COVID-19 variants, experts have continued to question how well the vaccines protect against these new strains. Now, researchers are trying to answer that.

A November analysis, which was published in the journal Lancet Microbe, included data from 24 studies to try to determine the level of immunity offered by COVID-19 vaccines against several virus variants.

The researchers found that the vaccines were less effective against what the World Health Organization classifies as COVID-19 variants of concern: Alpha, Beta, Gamma, and Delta than they were against the original SARS-CoV-2. They found that antibodies induced by infection were less effective against variants of concern, too.

The researchers’ models also predicted that the vaccines’ efficacy against variants over time could drop below 50% within the first year after vaccination. Over time, they saw a drop in neutralizing antibodies.

This, they concluded, suggests that booster doses of the COVID-19 vaccine are extremely important for populations as a whole to keep immunity against the virus. If people don’t get boosters, the researchers argued, protection from symptomatic COVID-19 could drop below 50% after six months. As a result, more people could get infected.

“It is likely that new COVID-19 variants will continue to emerge, as we have seen with Delta, with varying transmissibility and severity. Vaccines may not work as well against some of these variants,” Jamie Triccas, PhD, a professor of medical microbiology at the University of Sydney, said in a press release. “Essentially, we can predict how current vaccines will work against new variants, and test the efficacy of new vaccines, based on the results of small clinical trials that measure antibody responses. That’s a huge win for the battle against COVID-19.”

We're already seeing the rise of new virus variants, with reports of Omicron now spreading globally. As experts learn more about this new variant, they'll need to learn how vaccines hold up against its mutations.

But still, while vaccine immunity wanes over time, the researchers pointed out that protection against severe COVID-19 and death from the virus will likely stay high in the first year after someone is vaccinated.

"Optimal timing for boosters will depend on the availability of boosters, and whether the aim is to reduce overall case numbers or reduce the burden on the health system,” Deborah Cromer, PhD, lead study author from the University of New South Wales Sydney’s Kirby Institute, said in a statement. 

What Other Research Shows

Amesh A. Adalja, MD, an infectious disease expert and a senior scholar at the Johns Hopkins Center for Health Security, told Verywell that it’s “not surprising” that the most recent meta-analysis shows that the vaccine’s ability to protect against symptomatic COVID-19 wanes with time.

Richard Watkins, MD, an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University, agrees. “The finding of the study mirror what is being seen in clinical practice, namely, that immunity wanes over time,” he told Verywell.

Research has repeatedly shown that the effectiveness of the COVID-19 vaccines reduces over time. One small study of public health data from Israel published in The Lancet in July estimated that the Pfizer-BioNTech vaccine was 39% effective at keeping people from getting COVID-19 in June and early July—a significant drop from the 95% protection they had from January to early April. Still, the researchers found, the vaccine was more than 90% effective at preventing severe disease in people, even during the summer as the Delta variant spread widely.

A study published in The Lancet analyzed data from 728,321 people in Israel who either had a third dose of the COVID-19 vaccine or the standard two-dose administration. The researchers found that the vaccine’s effectiveness was 93% after five months for those who received three doses.

The researchers concluded that having a third dose of an mRNA COVID-19 vaccine is “effective in protecting individuals against severe COVID-19-related outcomes, compared with receiving only two doses.”

Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, told Verywell that “it makes sense” that people may be able to get a year’s worth of protection with a booster shot.

“We can an annual flu shot booster as well,” he pointed out. “It’s not a big to-do if we need to get an annual booster for COVID.”

But, Russo said, “we have to track things out to see how long neutralizing antibodies last after this booster shot. It may be more than a year.”

This All May Change

Adalja said that it’s important for people to remember that the current COVID-19 vaccines are the first of their kind. “There are going to be second-generation vaccines for which this type of analysis may not necessarily apply because they may induce more and different types of immunity,” he said.

Adalja said that “there may be a role for additional doses, particularly in those with high-risk conditions at a very frequent interval like a flu vaccine, but maybe less so for those without high-risk conditions.” But, he added, “second-generation vaccines will likely have different properties and possibly not have the same frequency of dosing.”

Currently, vaccine manufacturers like Moderna and Pfizer are already developing these second-generation vaccines. Some are even aimed at specific viral variants.

Russo noted that it’s important for doctors and scientists to keep tracking the data to see how often booster doses will be needed. “At the end of the day, real-world rules,” he said.

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