Many recent studies reporting on COVID-19 vaccines' safety, effectiveness

New studies looked at the safety of the adenovirus COVID-19 vaccines, the effectiveness of almost all the vaccines, and the impacts of COVID-19 infection in pregnancy and on long-term cardiac function. A physician columnist addressed pandemic-related anger.


A safety monitoring analysis of the Janssen (Johnson & Johnson) vaccine summarized all reactions reported in the time that nearly 8 million doses were administered. Published in the May 7 MMWR, it found that 97% of reported reactions were nonserious, but there were 17 thrombotic events with thrombocytopenia. “The safety profile thus far of the Janssen COVID-19 vaccine is similar to that observed in clinical trials. A rare but serious adverse event occurring primarily in women, blood clots in large vessels accompanied by a low platelet count, was rapidly detected by the U.S. vaccine safety monitoring system,” the authors wrote. Another article in the same MMWR reported on anxiety-related events after receipt of the Janssen vaccine. The analysis of five mass vaccination sites found a total of 64 anxiety-related events, including 17 cases of syncope. An analysis of the AstraZeneca vaccine in Denmark and Norway, published by The BMJ on May 5, found an increase in venous thromboembolic events: 59 in vaccine recipients versus the 30 that would normally be expected.

Studies of the Pfizer-BioNTech vaccine found that it significantly reduced both asymptomatic and symptomatic infections in Israeli health care workers, health care workers at St. Jude Children's Research Hospital in Memphis, Tenn., and the Israeli general population. The first two studies were published by JAMA on May 6, and the third was published by The Lancet on May 5. On May 10, the FDA expanded the emergency use authorization for the Pfizer-BioNTech vaccine to include adolescents 12 to 15 years of age.

Full vaccination with the Pfizer-BioNTech or Moderna vaccine was 94% effective against COVID-19–associated hospitalization in adults ages 65 years or older, while one shot was 64% effective, according to a report in the May 7 MMWR looking at U.S. hospitalizations in January through March. The effectiveness of either mRNA vaccine among recipients of solid organ transplant was analyzed in a study published by JAMA on May 5. It found that 54% of recipients had an antibody response after the second dose, but antibody levels were much lower than in immunocompetent patients, leading the authors to conclude that “a substantial proportion of transplant recipients likely remain at risk for COVID-19 after 2 doses of mRNA vaccine.”

Several recent studies also looked at the effectiveness of COVID-19 vaccines against virus variants, including a trial of the Novavax vaccine candidate in South Africa and an analysis of the Pfizer vaccine in Qatar, both published by the New England Journal of Medicine on May 5.

In other COVID-19 research, a study published by Annals of Internal Medicine on May 11 used a health care database to compare outcomes in hospitalized COVID-19 patients by whether they were pregnant or not, finding inpatient mortality rates of 0.8% (n=9) and 3.5% (n=340), respectively. A study published by JACC: Cardiovascular Interventions on May 8 looked for long-term cardiovascular effects of mild COVID-19 infection in otherwise healthy people. Using cardiac MRI and blood testing, it compared 74 health care workers who had recovered from COVID-19 at least six months before to 75 seronegative controls and found no differences in cardiac structure, function, tissue characterization, or biomarkers.

Finally, in his latest KevinMD column , ACP's Vice President of Membership and Global Engagement, Philip A. Masters, MD, FACP, shares his feelings about how COVID-19 has affected just about everyone in some way. Dr. Masters writes: “The profound uncertainty posed by COVID-induced cataclysms and the cultural, civil, and political unrest we've experienced over the past year has significantly skewed our sense of normalcy and well-being. Thus, responding with anger to these rapidly evolving and unpredictable circumstances isn't at all surprising.”