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COVID vaccines are not meant to prevent all infections, experts say. Americans need to reset their expectations.

USA TODAY logo USA TODAY 4/17/2022 Adrianna Rodriguez, USA TODAY
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Denny Mitchell couldn’t believe he tested positive for the coronavirus in January.

The 45-year-old from Houston never left the house without his mask, he avoided indoor dining at all costs, and most important, he was fully vaccinated. But he still got sick. 

“I was surprised because I was taking so many precautions,” he said.

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It’s no longer unusual to hear of someone getting COVID-19 even though they’re fully vaccinated and boosted. Yet, many Americans are still shocked when it happens to them. 

Early data showed the mRNA vaccines were highly effective against infection, but experts say the virus has changed over time and people need to reconfigure their expectations. The vaccines may not prevent all infection, but they still protect against the worst consequences of the disease.  

The Moderna Covid-19 vaccine is prepared for administration ahead of a free distribution of over the counter rapid Covid-19 test kits to people receiving their vaccines or boosters at Union Station in Los Angeles, California on January 7, 2022. - Los Angeles County reported more than 37,000 new coronavirus cases on January 6, breaking records again as a regional surge of the Omicron variant continues. (Photo by Frederic J. BROWN / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images) © FREDERIC J. BROWN, AFP via Getty Images The Moderna Covid-19 vaccine is prepared for administration ahead of a free distribution of over the counter rapid Covid-19 test kits to people receiving their vaccines or boosters at Union Station in Los Angeles, California on January 7, 2022. - Los Angeles County reported more than 37,000 new coronavirus cases on January 6, breaking records again as a regional surge of the Omicron variant continues. (Photo by Frederic J. BROWN / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images)

“That’s what we need to emphasize,” said Dr. Philip Chan, an infectious disease specialist and an associate professor at Brown University. “The fact that these vaccines are still effective against these emerging variants – in terms of severe disease, hospitalizations and death – is definitely a public health win.”

Americans’ high expectations of the COVID-19 vaccine stem from initial clinical trials in 2020 by Pfizer-BioNTech and Moderna, health experts say.

For the vaccines to obtain emergency use authorization from the Food and Drug Administration, they had to be 50% effective against infection; the main goal was to prevent severe illness and death. 

But the effectiveness of the mRNA COVID-19 vaccines was astounding. In trials involving more than 70,000 people, researchers found they were more than 90% effective against infection. 

Health experts were overcome with “sheer joy,” said Jodie Guest, professor and vice chair of the department of epidemiology at Emory University’s Rollins School of Public Health.

“We just couldn’t believe that they were working so great,” she said. “The amazement about it was really why we talked about that so much.”

Scientists expected to see changes in the vaccines’ effectiveness when they were used by millions of Americans and given to populations that weren’t included in the study, such as pregnant people and those with immunocompromising conditions.

What they didn’t expect, however, was the barrage of variants that quickly emerged, some of which, like omicron, were more transmissible and better able to evade the vaccines. Health experts had a hard time communicating the shifting reality to the public, said Andy Pekosz, a virologist at the Johns Hopkins Bloomberg School of Medicine.

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“We were letting the data drive the conversation … because we really didn’t know anything about what the variant would change,” he said. “When the vaccine efficacy went down, we may not have done as good a job of explaining why and putting the blame on the virus as opposed to putting the blame on the vaccine.”

Unlike measles or polio, which are caused by stable viruses, the SARS-CoV-2 virus that causes COVID-19 has dozens of strains, said Dr. John Swartzberg, a professor emeritus of infectious diseases at the University of California, Berkeley, in the school of public health.

“We have been using the measles vaccine since the late 1960s, and the virus hasn’t changed. That’s why we have been able to eliminate measles in the U.S.,” he said. The coronavirus “is able to change and drift from that protection we have. That’s a major reason why we’re seeing problems with these vaccines.

“SARS-CoV-2 is just a lot more formidable and a lot smarter than measles and polio.”

By April 2021, the number of infections in vaccinated people was so common that the CDC stopped tracking them. But some studies suggests these so-called breakthrough infections already were on the rise.

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A study in Washington State of 4 million vaccinated people showed that from January to August 2021, about 1 in every 5,000 experienced a breakthrough infection. When the delta and omicron variants emerged, health experts say, that rate may have increased to as high as 1 in 100.

The early public health messaging and the new reality of increased breakthrough infections may have undermined confidence in vaccines and affected booster uptake, Pekosz said.  

“You would have thought that anybody who got the vaccine would line up for the booster as well,” he said. “But we’re seeing across the country booster rates are much lower than the initial vaccination rates.”

COVID-19 boosters have been authorized for adults since November, but CDC data shows fewer than 50% of eligible Americans have received their first booster.

Mitchell, who completed his primary vaccine series last May, said he delayed getting boosted after his bout with COVID-19 because he wasn’t convinced more vaccine would protect him.

“(I) still don’t know how good or effective the vaccines are,” he said. “I have friends who were boosted and had a much worse experience (with COVID-19) than I did.”

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Studies show, however, that boosters are highly protective against serious disease.

A CDC study published in January found that during the delta and omicron waves a booster was 94% effective against emergency department visits and 82% effective against urgent care encounters. Researchers also found a third dose was up to 94% effective against preventing hospitalizations.

“It’s really clear that boosters expand how broad your immunity is,” Pekosz said. “Vaccines combined with infection give you an even stronger protection.”

Another CDC study published Tuesday found a booster dose was more than 57% effective against hospitalization after reinfection during the delta wave and nearly 68% effective during the omicron wave.

BA.2, a subvariant of omicron, made up more than 85% of new coronavirus cases last week, CDC data shows. The new strain may be more transmissible but appears to behave similarly to the original omicron variant, health experts say.

As cases steadily climb throughout the country, Chan said, he expects more breakthrough infections and emphasizes the importance of vaccines and boosters to stave off serious illness. 

“Public health and clinical medicine have to do a better job highlighting the positive aspects of these vaccines that really do prevent hospitalization, severe disease and death."

Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT. 

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: COVID vaccines are not meant to prevent all infections, experts say. Americans need to reset their expectations.

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