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COVID-19 vaccine booster shots are coming. Here’s what to know

People with weakened immune systems can already get a booster, but the benefit to everyone else is unclear.

This story has been updated to include a research study and a Food and Drug Administration document released Wednesday.

As interest in COVID-19 booster shots grows, there’s still a lot of uncertainty about getting a third dose.

President Joe Biden announced that third doses of the Pfizer and Moderna vaccines would be available to Americans, with a rollout starting Sept. 20. But that came before any recommendation from the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices and approval from the U.S. Food and Drug Administration. The CDC has still not voted to recommend booster doses.

Despite some pushback, Biden has reiterated that — pending regulatory approval — booster shots will be available to everyone about eight months after their second dose.

Then, on Monday, a group of international experts, including FDA and World Health Organization scientists, published a commentary in The Lancet saying there wasn’t enough evidence to support boosters for the general population.

The FDA is meeting on Sept. 17 to review whether the data supports booster doses for the Pfizer vaccine. Moderna has applied for FDA approval of a half-dose booster shot, so people who received the Moderna vaccine are unlikely to get a booster in September, the Associated Press reported.

Here’s what scientists and public health experts know so far about COVID vaccine boosters.

Do scientists think that a third shot is necessary?

People who have weakened immune systems — or are immunocompromised — are less likely to have developed a sufficient level of antibodies against the coronavirus from the two doses of the Pfizer and Moderna vaccines, studies show.

A third dose boosts the number of antibodies that immunocompromised people produce, which could bring this population closer to “fully vaccinated” status, according to preliminary research.

“I think it is important that the immunocompromised population has access to the booster, and I appreciate [having] that opportunity both personally and professionally,” said Erin Carlson, the director of graduate public health programs at the University of Texas at Arlington.

Erin Carlson is associate clinical professor and director of graduate public health programs at the University of Texas at Arlington's College of Nursing and Health Innovation.
Erin Carlson is associate clinical professor and director of graduate public health programs at the University of Texas at Arlington's College of Nursing and Health Innovation.(Lisa Torres)

Carlson, who has rheumatoid arthritis and takes immunosuppressive drugs, recently received her third dose of the COVID vaccine.

This extra dose helps protect those who are most vulnerable to severe illness. About 2.7% of U.S. adults self-report as immunocompromised. “The diseases we have… are not always visible to others,” she said, “and so people don’t know to be more careful around us.”

Protecting this population is also important for public health. “If we have not been fully vaccinated,” she said, “then we’re more likely to be able to transmit the virus to others.”

Grapevine resident Kerry Gunnels, who got his COVID vaccine as soon as he was eligible, said his decision to seek out a booster was an easy one. He started looking into where he could find a booster after he heard that scientists were saying they could extend the protection offered by the vaccines.

Gunnels, 70, a former Dallas Morning News editor, has diabetes, high blood pressure and an irregular heartbeat. “My conviction from the very beginning of COVID,” he said, “was that if I got [the virus], I was a dead man.”

He walked into a local compounding pharmacy on a Friday afternoon last month. When asked if he qualified for a booster, he listed off his underlying health problems. The pharmacist then prepared his third Moderna shot.

Gunnels, who continues to wear a mask, said he doesn’t regret getting a booster shot. “I’m still quite concerned about [getting COVID],” he said. “But I have done everything that I can do at this point to protect myself. And that is a comfort.”

But whether the general population would benefit from a third dose is a more complicated and unresolved question.

Deepta Bhattacharya, a professor of immunobiology at the University of Arizona College of Medicine, said it’s clear that a booster could be beneficial. A booster, he said, might reduce the chance that a person would get infected and develop symptoms.

What’s less clear is how much a national booster strategy would help control the spread of the coronavirus. “It just doesn’t seem like vaccinated breakthrough infections are the major source of transmission,” he said.

“If you don’t have a replicating virus, you don’t have transmission,” said Dr. Francesca Torriani, a professor of medicine in the infectious diseases division at the University of California San Diego.

This is why first doses of the vaccine really matter both domestically and globally. WHO has repeatedly called on wealthy nations to stop their plans for boosters.

Cecilia Tomori, the director of global public health and community health at Johns Hopkins University School of Nursing, said it will be important to ramp up global vaccinations by increasing production and waiving intellectual property rights of vaccine manufacturers. This could drive down virus transmission and improve U.S national security.

Who’s eligible for a booster now?

Currently, the CDC only recommends COVID vaccine boosters for people who are moderately to severely immunocompromised.

This includes people who have received an organ transplant or stem cell transplant, people with advanced HIV, people receiving treatment for blood cancers and people taking high-dose corticosteroids or other immunosuppressive medications.

People who are immunocompromised can get a booster shot if they are at least four weeks past their second Pfizer or Moderna dose. They can get the third dose anywhere vaccines are available. About 1 million booster doses have already been administered, according to reporting from The New York Times.

The rollout for the single-dose Johnson & Johnson vaccine started in March — several months after the two-dose mRNA vaccines. Last week, Johnson & Johnson said it had preliminary results from a small clinical trial. In the trial, people received a second dose of the vaccine six months after their first dose. The data has indicated some benefit to the booster but has not yet been peer-reviewed or published in a study.

Bhattacharya said he thinks most immunologists feel it’s likely that people who got this shot might need some form of booster.

How are scientists thinking about and measuring the effectiveness of the vaccines?

Scientists are thinking about the effectiveness in two main ways. The first is at the level of the immune response, which is mainly being measured by antibody levels.

“When people just look at antibody levels and say that there’s waning, I think that’s a little bit problematic and it doesn’t really capture what the immune response normally does,” Bhattacharya said.

In almost every type of immune response, he explained, immune cells produce an initial wave of antibodies early after vaccination. Immunologists say the quality of those antibodies at the beginning is pretty poor.

He said this response is thought to be a way of generating a lot of antibodies to try to keep things under control at the beginning. Then those antibodies are gradually replaced by a fewer number of high-quality antibodies, ones able to stick to the virus better.

“If you just look at the total antibody levels, it looks like they decline,” he said. “But you don’t really lose a proportionate amount of protection, because those poor antibodies are being replaced by better ones.”

Even if the virus does manage to slip past the antibodies, the immune system is much better prepared to deal with it. He said other memory immune cells quickly make a whole bunch of additional antibodies and kill any virally infected cells.

“All of these different layers of defense,” he said, “cooperate to keep the virus under control.”

The second way that scientists are evaluating vaccine effectiveness is by examining the overall number of COVID cases, the rate of infection and the rate of vaccination. But Torriani said that when assessing vaccination rates, it’s important to consider the entire population that is susceptible to disease, not just those who are eligible for the vaccine.

What’s the evidence for “waning immunity”?

Scientists say it’s unclear whether the effectiveness of the vaccines wanes over time, and they disagree over whether COVID-19 booster shots might be necessary.

If the two-dose series of the Pfizer vaccine is still effective in preventing hospitalizations and deaths from COVID, then the benefit of booster doses would probably be more limited, FDA staff said in a briefing document released Wednesday.

The FDA staff emphasized that all the COVID vaccines still protect against severe illness and death.

Other top health officials, including Dr. Anthony Fauci, have said a goal of booster doses would be to reduce the number of breakthrough infections and potentially reduce transmission, according to reporting by Reuters. Fauci is director of the National Institute of Allergy and Infectious Diseases and the chief medical advisor to President Joe Biden.

Last month, vaccine data from Israel seemed to indicate a higher-than-expected number of infections in people who were fully vaccinated with the Pfizer vaccine. A study published Wednesday in The New England Journal of Medicine indicated that people over the age of 60 who received a booster were less likely to test positive for COVID or develop severe illness than those who did not receive the booster.

Several recent studies in the U.S. have also suggested that vaccine effectiveness seems to have decreased slightly. Data from the public health department in the state of New York showed that between May 1 and July 25, vaccine effectiveness against infection dropped from 91.7% to 79.8%.

In a recent commentary in The New England Journal of Medicine, Torriani and her colleagues examined the rate of symptomatic COVID infections in UC San Diego health care workers. They found that in July, even though 86.7% of health care workers were fully vaccinated, vaccine effectiveness dropped from 94.3% to 65.5%.

The COVID “attack rate” also was higher in people who completed their vaccination series in January or February at 6.7 cases per 1,000 people compared with 3.7 cases per 1,000 people for those who completed vaccination between March to May. This suggests that immunity is waning but still protective, Torriani said.

But the emerging data about breakthrough infections in people who were fully vaccinated still indicates that the vaccines protect against severe illness requiring hospitalization and against death, researchers say. A recent CDC study found that unvaccinated Americans were 4.5 times more likely than vaccinated people to become infected with the virus, 10 times more likely to be hospitalized and 11 times more likely to die from the virus.

In Los Angeles, about a quarter of new coronavirus infections from May 1 to July 25 were in people who had been fully vaccinated, another CDC study found. However, unvaccinated people were 29 times more likely to be hospitalized than those who were fully vaccinated.

“The purpose of the COVID vaccine was not to stop transmission,” Carlson said. “It was to stop severe disease — to stop hospitalizations and deaths.”

This is why other COVID safety measures — like universal masking policies, improved indoor ventilation standards and frequent testing — are important, scientists say.

Torriani and her colleagues point to the increase in COVID cases among health care workers at UC San Diego as coinciding with California dropping its statewide mask mandate, the dominance of the delta variant and high levels of what the CDC defines as community transmission.

What do public health experts think the challenges are to getting a third dose into people’s arms?

Tomori of Johns Hopkins worries about how boosters will affect the vaccine divide. Researchers who focus on equity in public health emphasize that availability is not the same thing as accessibility.

She said there’s a group of highly motivated people who know a lot about the benefits of vaccination and were the first in line to receive the vaccine. This group tends to have higher health literacy and more access to information, she said.

“It does tend to be a more privileged group of people,” she said. “I think they’ll be lining up for their boosters.”

She said it’s not clear whether the people who are more vulnerable to COVID, especially those from marginalized communities, will be able to get adequate information they need. “From a public health perspective,” she said, “you want to center your strategy around people who are most vulnerable.”

Carlson emphasized: “The priority for the healthy, general population needs to be: Get vaccinated. Period. We still cannot let up on our resources being directed towards getting people vaccinated.”

Connect with needs and opportunities from Get immediate access to organizations and people in the DFW area that need your help or can provide help during the Coronavirus crisis.

Alejandra Canales, Special contributor. Alejandra Canales is a freelance science reporter for The Dallas Morning News and a graduate student in neuroscience at the University of Wisconsin-Madison. In summer 2021, she covered science for The News as part of a fellowship through the American Association for the Advancement of Science.

alejandra.canales@dallasnews.com @AllieCanales1
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