U.S. Adults to Be Offered COVID Booster Shots in September

The Biden administration announced a plan for U.S. adults who received either Pfizer or Moderna's COVID-19 vaccine to receive booster shots starting in late September.

"Having reviewed the most current data. It is now our clinical judgment that the time to lay out a plan for COVID-19 boosters is now," said Surgeon General Vivek Murthy, MD, MBA, during a briefing of the White House COVID-19 Response Team on Wednesday. "Recent data makes clear that protection against mild and moderate disease has decreased over time."

This decline in protection appears to be due both to waning immunity and to the strength and pervasiveness of the Delta variant, he said.

"Even though this new data affirms that vaccine protection remains high against the worst outcomes of COVID, we are concerned that this pattern of decline we are seeing will continue in the months ahead, which could lead to reduced protection against severe disease, hospitalization, and death," Murthy said.

According to a joint statement from the CDC, FDA, NIH, and National Institute of Allergy and Infectious Diseases that laid out the details of the administration's plan, the boosters will be offered starting the week of September 20 to U.S. adults who received their second mRNA dose at least 8 months earlier.

"We are not recommending that you go out and get a booster today," Murthy clarified. The first shots will be given to people vaccinated earliest in the rollout: healthcare providers, residents and staff at long-term care facilities, and other seniors.

The plan is contingent on both the FDA completing an independent review of the safety and effectiveness of a third dose of the Pfizer and Moderna mRNA vaccines and on the CDC's Advisory Committee on Immunization Practices (ACIP) recommendations after review of the evidence, the joint statement explained.

"Our plan is to protect the American people and to stay ahead of this virus," said CDC Director Rochelle Walensky, MD.

In explaining the new decision, she offered three key points: vaccine-induced protection does decline over time, effectiveness against hospitalization and death "remains relatively high,"and the vaccines are generally less effective against Delta.

New CDC data released in the Morbidity and Mortality Weekly Report (MMWR) on Wednesday showed that in New York state, vaccine effectiveness against infection declined from 91.7% to 79.8% from the period of May 3 to July 25, as the Delta variant became dominant. Effectiveness against hospitalization, however, was stable (91.9% to 95.3%).

Another MMWR of long-term care facilities in CDC's National Healthcare Safety Network reported declining effectiveness of the mRNA vaccines during Delta, dropping from an adjusted effectiveness rate of 74.7% pre-Delta (March to May) to 53.1% during the period of Delta (June-July).

Walensky also cited a previously reported analysis of Mayo Clinic data that demonstrated declining effectiveness of the mRNA vaccines against COVID-19 infection as the Delta strain took hold, though protection against hospitalization and ICU admission remained high.

"Taken together, these data confirm that while protection against infection may decrease over time, protection against severe disease and hospitalization is currently holding up pretty well," said Walensky.

"Preliminary data" from two vaccine cohort effectiveness studies involving more than 4,000 healthcare personnel, first responders, and other frontline workers at eight different sites indicated "waning effectiveness against symptomatic and asymptomatic infection ... from 92% prior to Delta to 64% with Delta," Walensky added.

The effectiveness decreased against Delta, regardless of when an individual was vaccinated, she noted. "These data suggests full vaccination in the context of the Delta variant may be correlated with less protection against SARS-CoV-2 infection than against prior variants."

NIAID Director Anthony Fauci, MD, presented the immunological argument for recommending a third vaccine dose.

He said that "regardless of the variant," antibody levels decline over time in fully vaccinated people, highlighting a recent study in Science. Higher antibody levels, meanwhile, are associated with better protection, he said, citing a recent preprint.

Importantly, boosters with the Moderna vaccine have been shown to increase antibody titers by "at least 10-fold, and likely much more," said Fauci, adding that Pfizer has shared "similar data."

"So you get a dramatic increase in antibody titers when you do a third immunization dose," he said. Altogether, the current studies "support the use of a third booster mRNA immunization to increase the overall level of protection."

The new guidance on boosters is restricted to recipients of Pfizer or Moderna's COVID shots, and do not apply to individuals who received the Johnson & Johnson vaccine, the rollout of which began later than the mRNA vaccines.

"We expect more data on J&J in the coming weeks," said Murthy. "With those data in hand, we will keep the public informed with a timely plan for J&J booster shots."

Murthy and other members of the response teams continued to underscore the urgency of getting shots to unvaccinated Americans and people around the world, given that virtually all cases that have led to severe disease, hospitalization and death occurred in unvaccinated people.

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