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Experts are trying to figure out if a COVID-19 booster shot will help fight the pandemic. Scott Olson/Getty Images
  • Israel and other countries are rolling out third doses of COVID-19 vaccines to people fully vaccinated. But more research is needed on the benefits and timing of booster doses.
  • Germany plans to start offering booster doses in September to older adults and people with weakened immune systems. The United Kingdom will also begin its own booster rollout next month.
  • The United States has yet to fully embrace COVID-19 boosters.

As Delta variant surges threaten to erode pandemic progress, some highly vaccinated countries are offering booster doses of COVID-19 vaccines to their citizens.

This week, Israel began administering third doses of the Pfizer-BioNTech vaccine to people over age 60 who are already fully vaccinated, reports the Associated Press.

According to Reuters, Germany plans to start offering booster doses in September to older adults and people with weakened immune systems. The United Kingdom will also begin its own booster rollout next month.

The United States has yet to fully embrace COVID-19 boosters, but it’s edging in that direction.

As recently as early July, the Centers for Disease Control and Prevention (CDC), along with the Food and Drug Administration (FDA), said “Americans who have been fully vaccinated do not need a booster shot at this time.”

But the agencies added that they’re continuing to monitor the scientific data in order to decide if and when a booster might be needed.

However, Biden administration officials are warming to the possibility that older adults and immunocompromised people who’ve had two doses of an mRNA vaccine — Pfizer-BioNTech or Moderna-NIAID — might need a third dose.

In addition, the CDC’s Dr. Amanda Cohn said the agency is “actively looking into ways” to provide certain people access to booster doses “earlier than any potential change in regulatory decisions,” according to The New York Times.

The FDA would need to modify a vaccine’s current emergency use authorization (EUA) to allow a booster dose to be given. Another option would be full FDA approval, which would enable doctors to recommend a booster dose “off-label.”

The FDA could make a decision on full approval of the Pfizer-BioNTech vaccine by early September, reports the Times.

In anticipation of the potential need for boosters — in addition to vaccinating children under age 12 if the FDA approves the vaccines for this group — the U.S. government is bolstering its vaccine supply, reports Reuters.

Even as some countries roll out boosters, data on the need for an extra dose of the vaccines is limited, especially for the general public.

The clearest benefits are for those with weakened immune systems, such as people with cancer, organ transplant recipients, and older adults with chronic medical conditions.

These people might not generate as robust an immune response after vaccination, something the CDC warns about on its website.

“We’re probably going to have to be giving boosters to immunocompromised people and [other] people who are susceptible,” Dr. Ezekiel J. Emanuel, an oncologist at the University of Pennsylvania, said during an Infectious Diseases Society of America media briefing. “I think that’s where we’re going to start.”

For the rest of the population, the vaccine protection appears to hold up well at least for several months, even in the face of the Delta variant — although some studies suggest that some aspects of this protection may wane over time.

Data from Pfizer’s ongoing clinical trial found that the efficacy of its vaccine against symptomatic cases dropped from 96 percent to 84 percent during the 6 months after vaccination, according to a preprint released last week.

More than half of Americans vaccinated against the coronavirus have received Pfizer-BioNTech’s vaccine.

However, efficacy over 80 percent is still high — the FDA had initially set the efficacy bar for COVID-19 vaccines at 50 percent.

The Pfizer study also found that the vaccine continued to offer strong protection against severe disease — 97 percent efficacy — during the 6 months after vaccination.

Moderna released data in April showing that two doses of its vaccine had a 6-month efficacy of 90 percent against symptomatic cases and 95 percent against severe disease. The company didn’t provide any details on whether this changed over time.

It’s not clear if the drop in efficacy against symptomatic infection seen in Pfizer’s study is due to changes in the immune response, the spread of Delta and other variants during that time, or changes in people’s behaviors as pandemic restrictions were lifted.

Some studies have found that certain vaccines hold up well against the Delta variant, although the results have been mixed.

In a study published in The New England Journal of Medicine, researchers found that two doses of the Pfizer-BioNTech vaccine was 88 percent effective against symptomatic infection caused by the Delta variant.

This was lower than the 94 percent protection offered against the Alpha variant.

However, recent data from Israel, which has fully vaccinated more than 62 percent of its population, suggests a larger drop in protection.

Data from the Israeli Ministry of Health showed that between June 20 and July 17, the Pfizer-BioNTech vaccine was 39 percent effective against infection caused by Delta, reports Bloomberg.

This low protection was a shock to many.

Dr. Anthony S. Fauci, who heads the infectious disease division of the National Institutes of Health, said the low effectiveness had people “raising their eyebrows a bit,” reports the Times. He added that he would like to compare this to similar data being collected by the CDC.

As with other studies, though, the Israel data still showed strong protection — 91 percent — against severe illness caused by Delta, with 88 percent effectiveness against hospitalization.

While any drop in protection offered by a COVID-19 vaccine should be closely monitored, experts say the need for boosters would depend on how well the vaccines still protect people against severe disease.

This will require ongoing real-world monitoring of the effectiveness of the vaccines, like the data being collected regularly by the Israeli government and CDC.

In addition, scientists will continue to monitor antibody levels and other markers of immune protection in people who have been fully vaccinated to see how these change over time.

Vaccine makers are already studying the benefits of booster doses, with a focus on variants of concern.

Pfizer released data in an earnings report last week suggesting that a third dose of its vaccine “strongly” enhances protection against the Delta variant.

The data showed that people ages 18 to 55 who received a third dose of the vaccine had more than fivefold higher levels of antibodies that target the Delta variant, compared to levels after the second dose.

In people ages 65 to 85, the third dose boosted Delta-specific antibodies more than 11-fold.

These data were released as part of Pfizer’s quarterly earnings report and haven’t been peer-reviewed.

It’s not clear whether the higher levels of antibodies reported by Pfizer translate to greater protection, or if the level of antibodies provided by two doses is sufficient.

To know this, a clinical trial is needed. The company started one recently which will look at whether people who receive a third dose are better protected against the coronavirus in the real world, compared to those with only two doses.

The company also said in its quarterly report that it plans to request FDA emergency approval for a booster dose as early as August.

Even with the shortage of data on the benefits of boosters, some people are seeking them out on their own at local pharmacies, in other states, and in other countries — wherever there’s no record of their original vaccination.

Some of this stems from concerns about the spread of the Delta variant.

The FDA’s Dr. Peter Marks said on Tuesday that the agency “does not recommend taking things into your own hands” regarding COVID-19 vaccine booster doses.

“It’s actually not something you’re supposed to do under emergency use authorization,” he said during a discussion hosted by the COVID-19 Vaccine Education and Equity Project briefing.

With Delta surges happening throughout the United States, but especially in areas with low vaccination rates, Emanuel thinks more efforts should be made to reach the third of eligible Americans who haven’t had a single dose.

“Way more important than [giving] boosters to people who have already been vaccinated twice is getting people who haven’t been vaccinated, fully vaccinated,” he said. “I think we need to put our priorities in the right place, as a country.”

Other health experts are concerned about wealthy countries rolling out boosters, while many low- and middle-income countries are struggling to vaccinate their citizens with first doses due to a lack of supply.

“So far, more than 4 billion vaccine doses have been administered globally. More than 80 percent have gone to high- and upper-middle income countries, even though they account for less than half of the world’s population,” World Health Organization Director General Dr. Tedros Adhanom Ghebreyesus said in a briefing.

Low vaccination rates in other countries put their most at-risk citizens in danger of hospitalization and dying from COVID-19.

But ongoing high transmission of the coronavirus also increases the chances that another variant of concern will emerge. This is also a concern in parts of the United States with low vaccination rates.

Ghebreyesus called for a moratorium on boosters until at least the end of September to allow all countries to vaccinate 10 percent or more of their population.