I am following the latest developments on COVID-19 and our efforts to control the pandemic or to deal with it as an endemic disease. As of April 17:
Second “Booster Dose” Helps to Protect People over 60: After two initial Pfizer vaccine doses and one booster dose, a study of 182,122 adults ages 60 and over showed that a second booster dose provided 52 percent protection against asymptomatic infection and 76 percent protection against COVID-related death 14 to 30 days after the booster was given (N Engl J Med, April 13, 2022). Protection against harm from COVID-19 increased as days after vaccination increased. The highest protection occurred at days 14 to 30 after receiving the second booster dose.
Boosters Reduce Hospitalization: The COVID-19 mRNA vaccines’ two-dose primary series appeared to provide less protection against hospitalization from Omicron variant infections than Alpha and Delta infections (JAMA, April 12, 2022;327(14):1323). A booster dose, however, was associated with increased effectiveness against Omicron hospitalizations at the same high levels achieved against earlier variants with two doses. The study included data from 11,690 adults admitted to 21 U.S. hospitals from March 11, 2021, to January 14, 2022. The two doses of vaccine increased prevention of hospitalization by 85 percent during Alpha and Delta infections, but only 65 percent during Omicron infections. Adding a third booster dose increased prevention of hospitalization to 86 percent. Vaccines reduced all types of COVID-19 severity significantly (BMJ, Mar 9, 2022; 376: e069761).
Most Reactions to COVID-19 Vaccine are Mild: The CDC reports that during the first six months of the U.S. COVID-19 vaccination program, most adverse events were mild and short-lived (Lancet Infectious Diseases, March 7, 2022). Almost 300 million mRNA vaccine doses were administered in the U.S. between December 14, 2020, and June 14, 2021 (JAMA, April 12, 2022;327(14):1323). Of the 340,522 reports of vaccine side effects, 92.1 percent were classified as non-serious; 6.6 percent as serious but not resulting in death; and 1.3 percent were deaths. The most common serious reports were shortness of breath, fever, fatigue, and headache. The most common causes of death was heart disease. The less serious reactions were more common after the second dose, compared to the first dose.
COVID-19 Vaccination Reduces Infectious Viral Load: Usually the more virus in a person infected with COVID-19, the more serious the disease. Viral load was measured in 600 infected symptomatic patients (Nature Medicine, April 14, 2022). The Delta variant caused a higher viral load than the original virus or the Omicron variant. Vaccination dramatically reduced viral load for Delta and Omicron infections, but a third booster dose was necessary for the Omicron infections. Omicron’s very high infectiousness is caused by factors other than viral load alone.
Dr. Gabe Mirkin is a Villager. Learn more at www.drmirkin.com