Many countries have commenced vaccination programs against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the coronavirus disease (COVID-19).
The rapid development of vaccines against SARS-CoV-2 offers a great promise of stemming the spread of the COVID-19 pandemic. Despite the efforts to deploy the vaccines in many countries, challenges to the supply chain have prompted questions about whether a single rather than double dose administration may be sufficient for some individuals.
Researchers at the Cedars-Sinai Medical Center in the U.S. assessed the SARS-CoV-2 antibody response following first and second doses of a messenger ribonucleic acid (mRNA) vaccine, Pfizer-BioNTech vaccine, administered in a large and diverse group of healthcare workers.
The researchers found that people who were previously infected with SARS-CoV-2 developed a level of provoked antibody response, even after receiving just one dose of the vaccine. The immune response is comparable to the provoked response seen after a two-dose vaccination course administered to infection naïve individuals.
In the study, published on the pre-print medRxiv* server, the researchers evaluated the immune response in a cohort of 1,089 healthcare workers who received the Pfizer-BioNTech vaccine in Southern California.
The team evaluated and measured the circulating levels of SARS-CoV-2 anti-nucleocapsid (N) protein immunoglobulin G (IgG) and anti-spike (S) protein IgG at three-time points –before or up to three days after the first dose, within seven to 21 days after the first dose, and seven to 21 days after the second dose.
Further, they studied the proportion of vaccine recipients who attained the threshold after receiving one dose or two doses. Apart from these, the researchers obtained data from the participants on their medical history, if they were exposed to SARS-CoV-2, and symptoms they experienced after each vaccine dose.
The team also noted the history of COVID-19 infection, and timing was linked to the date of the first dose received. They then compared antibody levels and symptom responses between those with and without past COVID-19 diagnosis.
The recipients of the vaccine provided at least one blood sample for antibody testing. Of the recipients, 980 provided baseline samples, 525 provided samples after the first dose, and 238 provided samples after the second dose. Meanwhile, 216 recipients provided samples for all three-time points.
The team found that from the total sample, the proportions of anti-S IgG levels at or above the threshold were akin to COVID-19 recovered persons at baseline, compared to infection naïve individuals after a single dose.
Further, the study findings showed that COVID-19 recovered persons developed a level of provoked antibody response after just one dose of the vaccine. This is similar to the response seen after the two doses given to people who had never been infected.
The study suggests that giving at least one dose of the vaccine may provide a potential benefit, given that the pre-vaccine levels of anti-S IgG in COVID-19 recovered people to be lower than the levels found among those who were never infected following a single dose of the vaccine.
With the vaccine supply challenges and the aim of countries to vaccinate most of their population, providing a single dose could provide protection. However, the researchers reiterate that further studies are needed to validate their findings.
If validated, an approach that involves providing a single dose of vaccine to persons with a confirmed history of COVID-19 infection along with an on-time complete vaccine schedule for infection naïve persons could assist with maximizing the benefit of a limited vaccine supply,” the researchers recommended.
COVID-19 vaccine rollouts
Many countries have already started administering vaccines to their citizens. Most of these countries prioritized healthcare workers and high-risk groups, including the elderly and those with comorbidities.
While vaccines are being distributed, health experts emphasize that infection control measures are still essential to prevent infection. These include regular handwashing, physical distancing, and the wearing of face masks.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.