COVID-19 survivors may be able to skip 2nd vaccine dose

COVID-19 survivors may not need a second dose of mRNA-based vaccine to prevent subsequent symptomatic infections, which could stretch limited vaccine supplies, reports a research letter published yesterday in the New England Journal of Medicine.

Researchers at the Icahn School of Medicine at Mount Sinai used a convenience sample from an ongoing study of 110 participants in the longitudinal Protection Associated with Rapid Immunity to SARS-CoV-2 (PARIS) study. All received one dose of the Pfizer/BioNTech or Moderna vaccine in 2020, although 39.0% were seropositive for COVID-19 antibodies prior to vaccination. Eighty-eight participants received the Pfizer vaccine, and 22 had the Moderna vaccine. Mean patient age was 40 years.

Most coronavirus-naïve participants had varied and relatively low immune responses in the first 9 to 12 days after each of the two doses. Those previously infected with COVID-19, however, had a robust immune response within days of receiving a single dose as well as after the second dose.

Higher antibody levels

Antibody concentrations against COVID-19 in coronavirus survivors were 10 to 45 times those of coronavirus-naïve participants at the same time points after receiving their first shot. Immune responses after the first dose didn't significantly differ between the Pfizer and Moderna vaccines.

Antibody levels increased threefold in participants not previously infected with COVID-19 after the second shot, but they didn't rise after the second dose in COVID-19 survivors. Regardless, those previously infected had more than six times the median antibody levels than coronavirus-naïve participants after the second dose.

Lead author Florian Krammer, PhD, said in a Mount Sinai Hospital news release that the findings show that a single dose of vaccine may be sufficient for COVID-19 survivors. "In fact, that first dose immunologically resembles the booster [second] dose in people who have not been infected."

COVID-19 survivors likely respond more strongly to the first vaccine dose because their immune cells have already learned to recognize the coronavirus's spike protein, according to the release. The authors said that the ongoing follow-up studies will show whether these early differences in immune responses are sustained over prolonged periods.

No serious adverse events

An analysis of local, injection-site related, or systemic reactions to the first dose in 230 participants from the larger PARIS study also showed that neither the Pfizer nor the Moderna vaccine produced serious adverse events requiring hospitalization. Of the participants, 82 had previously tested positive for COVID-19, while 148 had not.

One-hundred fifty-nine participants (69%) reported side effects after the first vaccine dose; 46% of them were in coronavirus-naïve participants, and 89% were COVID-19 survivors. The most common side effects were pain, swelling, and redness at the injection site, and the most-reported systemic adverse effects were fatigue, headache, chills, muscle pain, fever, and joint pain.

In the release, study co-author Viviana Simon, MD, PhD, suggested using a serological assay to detect antibodies in a patient with an unknown COVID-19 infection history before vaccination. "If the screening process determines the presence of antibodies due to previous infection, then a second shot of the coronavirus vaccine may not be necessary for the individual," she said.

"And if that approach were to translate into public health policy, it could not only expand limited vaccine supplies, but control the more frequent and pronounced reactions to those vaccines experienced by COVID-19 survivors."

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