One Dose of mRNA Vaccine May Be Enough for Older COVID-19 Survivors

One dose of an mRNA vaccine may provide adequate protection against coronavirus disease 2019 (COVID-19) among older adults previously diagnosed with COVID-19, a new study suggests.

The research letter, published in JAMA, evaluated 102 residents of 6 nursing homes in Montpellier, France, including 60 who had no prior COVID-19 infection, 36 who had a positive reverse transcriptase–polymerase chain reaction (RT-PCR) test and were seropositive for SARS-CoV-2 nucleocapsid (N) protein IgG in June 2020, and 6 who had either a positive RT-PCR result or were seropositive for SARS-CoV-2 nucleocapsid protein IgG.

The study was led by Hubert Blain, MD, PhD, of the Department of Internal Medicine and Geriatrics at Montpellier University of Excellence (MUSE) in Montpellier, France. All participants received a first dose of the BNT162b2 mRNA COVID-19 vaccine developed by Pfizer and BioNTech in January 2021. Levels of IgG antibody against the SARS-CoV-2 spike (S) protein were measured 3 weeks later.

Among the 36 with prior COVID-19 infection, 26 (72.2%) remained seropositive for nucleocapsid protein IgG in January-February 2021 and all were seropositive for S-protein IgG after 1 vaccine dose. Among the 60 participants with no history of COVID-19, 29 (49.2%) were seropositive for spike protein IgG after the first dose of the vaccine.

“This preliminary study suggests that a single dose of BNT162b2 vaccine may be sufficient to obtain a high level of S-protein IgG antibody in nursing home residents previously diagnosed with COVID-19 based on RT-PCR results,” the investigators wrote in their research letter.

The study was consistent with previous research led by Saman Saadat, PhD, Institute of Human Virology, University of Maryland School of Medicine, Baltimore, MD, which showed that health care workers with prior COVID-19 infection had higher antibody titer responses to a single dose of mRNA vaccine than those without prior infection.

“Measuring S-protein IgG antibody levels just before the second vaccine dose could be useful in determining whether a second dose is required in individuals whose infection history is unknown,” the research letter said. “This could limit possible adverse effects related to reactogenicity in previously infected patients and spare precious vaccine doses.”

The median level of spike protein IgG after vaccination was greater among those with prior COVID-19 diagnosis than among those without (40,000 AU/mL vs 48.0 AU/mL). Levels of spike protein IgG antibodies among the other 6 participants who had a positive RT-PCR result or who were seropositive for N-protein IgG also were significantly higher than those without prior infection.

Limitations of the study include its small size and lack of neutralization assays.

COVID-19 has disproportionately affected residents of long-term care facilities, who have accounted for 34% of COVID-19 deaths in the United States despite making up less than 1% of the country’s population.

A recent study found that the Pfizer-BioNTech vaccine is effective in controlling the spread of COVID-19 in skilled nursing facilities, protecting residents as effectively as the general population. Increased vaccination coverage among staff members was associated with a drop in new infections after the first dose of COVID-19 vaccine, another study found.