On Thursday, the U.S. Food and Drug Administration announced that it has authorised third Pfizer and Moderna shots for certain immunocompromised people, particularly organ transplant recipients and people diagnosed with conditions with “an equivalent level of immunocompromise.” This comes days after a randomised trial in Canada confirmed that, among 120 patients, three doses significantly boosted organ recipients’ immune response to the coronavirus. Study co-author Atul Humar told Gizmodo earlier this week that they expect third Moderna shots would help protect this vulnerable population against the highly contagious Delta variant.
In a July assessment of additional doses for immunocompromised people, the CDC cited 2013 data finding that less than 3% of Americans are immunocompromised. The CDC’s umbrella definition of “immunocompromised persons” covers solid organ transplant patients, as well as cancer patients on immunosuppressants; people living with HIV/AIDS; and genetic diseases such as congenital agammaglobulinemia. A CDC advisory committee is set to meet today to discuss more detailed recommendations about who exactly should get a third dose. Taking immunosuppressant medications often means that a person does not generate a strong antibody response after receiving a vaccine, compared to other people.
To be clear, this is less of a “booster” in the conventional sense; three shots may simply need to be the standard dosing for certain populations. In March, Johns Hopkins Medicine researchers only detected antibodies in 17% of fully vaccinated organ transplant recipients. Earlier this week, a leaked CDC briefing reportedly estimated that over one million people had received unauthorised third Pfizer and Moderna shots. STAT news has reported that people have been getting the extra shots through a physician or by lying about having already gotten vaccinated — which “puts the onus on hospital systems to make prescribing policies” and “on vaccination sites to check people’s vaccine records.”
For people who are not immunocompromised, two doses of an mRNA vaccine or one dose of the Johnson & Johnson vaccine still seem to offer strong protection against hospitalisation and death from the Delta variant, but Delta does seem to be better than past strains at “breaking through” and infecting vaccinated people. Thankfully, those breakthrough infections are unlikely to be serious.
The U.S. has been keeping a well-stocked vaccine supply in hopes that local vaccine holdouts would come around. But many countries are in desperate need of shots. While 50% of the U.S. population is fully vaccinated, only 16.1% of the human population at large has received a full dose, according to Our World in Data.
The Canadian study only assessed Moderna, but the Moderna and Pfizer shots are similar and are both based on mRNA. The researchers wrote that more study is needed on the optimal dosing strategy for other types of vaccines among immunocompromised people. In the U.S., most vaccinated people have received an mRNA vaccine, but the Johnson & Johnson shot is also authorised here.
In the FDA’s announcement, Acting FDA Commissioner Janet Woodcock urged: Don’t get another shot unless you need one. “As we’ve previously stated,” Woodcock said, “other individuals who are fully vaccinated are adequately protected and do not need an additional dose of COVID-19 vaccine at this time.” Woodcock adds that the FDA is still researching whether boosters will be needed and when. Health officials have repeatedly stated that there’s insufficient data to support the need for boosters for the general population.