Maryland doctors support decision to give third COVID-19 vaccine dose to those with weakened immune systems

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People who have had transplants, cancer treatment, advanced HIV or otherwise have weakened immune systems and can’t fight infections well can get another dose of COVID-19 vaccine, U.S. regulators confirmed Friday.

They will be the first people to gain access to a third dose of either the Pfizer-BioNTech or Moderna mRNA two-dose vaccines, but health leaders inside and outside government generally say other groups such as seniors and health care workers at increased risk from the virus will not receive boosters any time soon.


The U.S. Food and Drug Administration expanded the emergency use authorization for the two vaccines for immunocompromised people late Thursday and an influential advisory panel to the U.S. Centers for Disease Control and Prevention endorsed the move Friday.

“These were people who never really had a good response to begin with from a two-dose regime,” said Dr. Kathleen Neuzil, director of the Center for Vaccine Development and Global Health in the University of Maryland School of Medicine. “This is opposed to most of us getting a good response and maybe we get a booster down road to boost our waning immune response. We don’t want world going out and getting a booster dose.”


Neuzil participated in a working group that led up to Friday’s vote by the CDC’s Advisory Committee on Immunization Practices, which typically guides the agency and helps physicians and insurers determine how to use and pay for vaccines.

FDA officials said the situation was influenced by the risk of infection for immunocompromised people from the delta variant that has fueled a surge in COVID-19 cases and hospitalizations across the country.

“After a thorough review of the available data, the FDA determined that this small, vulnerable group may benefit from a third dose of the Pfizer-BioNTech or Moderna vaccines,” said Dr. Janet Woodcock, acting FDA commissioner, in a statement. “As we’ve previously stated, other individuals who are fully vaccinated are adequately protected and do not need an additional dose of COVID-19 vaccine at this time.”

She added that the FDA continues to study if and when others may need another dose of vaccine.

Neuzil said that is because eventually immunity will wane in people who have been vaccinated, though for now the vaccines remain highly effective. The University of Maryland School of Medicine is now conducting a “mix and match” trial to see whether using any vaccine for a booster dose would work to rebuild immunity.

The vaccines still are considered effective even against the delta variant, which is producing so-called “breakthrough” cases in vaccinated people. But most people who do get infected do not get sick enough to require hospitalization.

CDC Director Dr. Rochelle P. Walensky said some studies suggest fully vaccinated immunocompromised people account for a large proportion of hospitalized breakthrough cases, 40% to 44%, though they make up only about 3% of the U.S. adult population. They also are more likely to transmit the virus to others in the household.

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They do not need a doctor’s referral to get a third dose, but some health experts suggest that is a good idea.


Dr. Dorry Segev, a transplant surgeon and professor of surgery at the Johns Hopkins University School of Medicine, said fully vaccinated transplant patients have higher risk of getting COVID-19, being hospitalized and dying than other patients.

A third dose will help with “immune priming,” he said, which allows the immune system to view an intruder, create a response and go dormant until the intruder reappears. Multiple priming sessions among immunocompromised individuals is not uncommon, he said. For example, they often get higher doses of the flu vaccine.

”We clearly know the immune systems are purposefully suppressed, so their responses are going to be less dramatic than in the general population,” Segev said.

Some patients might need three doses, while others might need four or five, he said. Some also might need to adjust medications or treatment plans.

Segev has been running two large studies assessing transplant patients and those with autoimmune disorders and others who are immune suppressed. A new, $40 million study, launched this week in Baltimore and funded by the National Institutes of Health, also will examine transplant patients and supplemental shots.

”The people we’re talking about need more than two shots,” he said. “We’re not giving them excess vaccines. It’s absolutely reasonable for us to improve the vaccination status in people who need it.”