New recommendations for high-risk outpatients; data on omicron and boosters, breakthrough infections, myocarditis

On Jan. 19, the NIH's COVID-19 treatment guidelines panel updated its recommendations on therapies for high-risk outpatients with mild to moderate COVID-19, in response to the omicron variant's reduced susceptibility to monoclonal antibodies. The panel now favors the use of ritonavir-boosted nirmatrelvir (the Pfizer pill) in the most high-risk outpatients with mild to moderate COVID-19. If it is not available or cannot be used because of drug interactions, then the panel recommends sotrovimab. If sotrovimab is not available, the panel recommends remdesivir. Molnupiravir (the Merck pill) should only be administered when the other three options are either not available or cannot be used.

Multiple recent studies looked at the protective effect of a booster dose of mRNA vaccine against omicron. In a U.S. study of patients seeking testing due to COVID-19-like symptoms, published by JAMA on Jan. 21, receipt of three doses of an mRNA COVID-19 vaccine was associated with lower likelihood of infection with the omicron variant compared with no vaccination or two doses. The adjusted odds ratio for testing positive after three doses versus no vaccine was 0.33 (95% CI, 0.31 to 0.35) for omicron and 0.065 (95% CI, 0.059 to 0.071) for delta; for three doses versus two doses, the odds ratio was 0.34 (95% CI, 0.32 to 0.36) for omicron and 0.16 (95% CI, 0.14 to 0.17) for delta. Two CDC analyses, published by MMWR on Jan. 21, offered similar findings, showing the protective effect of a booster dose on risk of infection or mortality and hospitalization or medical visits during delta and omicron predominance.

ACP updated a set of its rapid practice points on COVID-19 on Jan. 25. The update, published by Annals of Internal Medicine along with a supporting evidence review, recommends clinicians not use SARS-CoV-2 antibody tests to diagnose SARS-CoV-2 infection or predict the degree or duration of natural immunity conferred by antibodies against reinfection. “Although natural immunity remains a topic of scientific interest, this topic is being retired from living status given the availability of effective vaccines for SARS-CoV-2 and widespread recommendations for and prevalence of their use,” the update said.

The protection against COVID-19 from vaccination versus previous infection was compared in a study published by MMWR on Jan. 19. It found that before delta became the predominant variant in June 2021, infections were higher among people who survived a previous infection than people who were vaccinated, but by early October, people with a previous infection had lower infection rates than people who were vaccinated alone. Another study, published by JAMA on Jan. 20, looked at infections among vaccinated people in the U.S. during delta's predominance. Breakthrough infections increased from July to November 2021 among recipients of either mRNA vaccine, but they were significantly more common with the Pfizer-BioNTech vaccine than the Moderna vaccine (hazard ratio, 0.85; 95% CI, 0.80 to 0.89).

Two studies looked at carditis associated with the vaccines. An analysis from Hong Kong, published by Annals on Jan. 25, found higher odds of carditis in recipients of the Pfizer-BioNTech vaccine than in unvaccinated people (adjusted odds ratio, 3.57; 95% CI, 1.93 to 6.60), mainly seen after the second dose. The authors noted that the absolute risk was low, at 0.57 cases per 100,000, and should be weighed against the benefits of vaccination. An analysis of reports to the Vaccine Adverse Event Reporting System, published by JAMA on Jan. 25, similarly found a risk of myocarditis after the second dose of mRNA vaccine, particularly in adolescent and young men. Assessment of 826 reported cases of myocarditis among those younger than 30 years of age found that 98% had elevated troponin levels and 72% had abnormalities on electrocardiogram or cardiac MRI; 96% were hospitalized and 87% of them had resolution of presenting symptoms by discharge. The most common treatment was NSAIDs.