Thread by @DrEricDing

📍BREAKING—the FDA is expected to authorize a third shot of Pfizer & Moderna #COVID19 vaccine as soon as Thursday for many people with weakened immune systems—to better protect them from the #DeltaVariant. This follows Israel—already started in July. 🧵
nytimes.com/2021/08/11/us/…

2) The expanded EUA covers people who have had solid organ transplants and others whose immune systems are similarly compromised. The development will give physicians latitude to recommend additional shots for those patients.

3) “At least 3 percent of Americans have weakened immune systems for a variety of reasons, from a history of cancer to the use of certain medications such as steroids.”

4) Studies suggest that patients such as organ transplant recipients are in between — often showing little immune response to the standard vaccine regimen, but benefiting from a third shot.

5) One recent randomized, placebo-controlled study by Canadian researchers found that a third dose of the Moderna vaccine improved the immune response of people in that group.

nejm.org/doi/full/10.10…

6) “Dr. Dorry Segev, at the Bloomberg School of Public Health at Johns Hopkins University, has said about **half of transplant patients have no antibody response** to the currently authorized vaccine dosage.

7) “His team studied 30 transplant patients who were vaccinated but had negative or low-positive antibody titers, which suggested a poor response by their immune systems to the shots. After an additional shot, 14 of them had higher antibody titers.

8) After the third dose, the median percent virus neutralization was 71% in the mRNA-1273 (Moderna) group and 13% in the placebo group, and % of patients >30% threshold for neutralizing antibody positivity was 60% and 25%, respectively (relative risk, 2.4; 95% CI, 1.5 to 4.0)