CDC’s Messonnier says no change in the Covid-19 vaccine regimen as we know it works

Messonnier: We can't stretch vaccine doses unless we know it works “We have to stick with what we know works,” Nancy Messonnier of the CDC told @HelenBranswell during a live virtual conversation today. Andrew Joseph STAT

In an effort to stretch the supply of Covid-19 vaccines, some have advocated for further spacing out the two doses required for some of the shots or, in the case of the Moderna vaccine, lowering the dosage given with each jab.

But Nancy Messonnier, the director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases, reiterated Tuesday that federal health authorities continue to stand behind the current recommendations about the timing and strength of the shots, which were proven to be protective in clinical trials. She added that regulators and officials would continue to review new data as it was released.

“We have to stick with what we know works,” she told STAT reporter Helen Branswell during a live virtual conversation. “This is the regimen that’s been carefully studied. We’ve promised the American public that we would follow the data and follow the science, and that’s what we’re doing.”

So far, U.S. regulators have authorized three Covid-19 vaccines, a one-shot immunization from Johnson & Johnson and two-dose regimens from Moderna and Pfizer-BioNTech. The interval between Moderna doses is 28 days; for the Pfizer shot, it’s 21 days.

Some lawmakers and scientists have called for extending that period to get more people an initial dose, a step that some other countries have pursued. They’ve also called for looking into giving a lower dosage of the Moderna vaccine, which, as given now, contains about three times as much vaccine as the Pfizer shot. The U.S.’s vaccine development program has asked Moderna to study if the dosage could be reduced without pinching the amount of protection it confers....