Immunity gained after natural infection from the acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is boosted when people take the first Pfizer-BioNTech vaccine, according to a new study led by Iain C. Chapple from the University of Birmingham.
The findings suggest vaccination could help people who are at high risk of contracting SARS-CoV-2 from their job, such as dental providers who have close exposure to patients' faces.
The research team observed an increased antibody response after the first vaccine shot compared to the antibodies measured from natural immunity.
"Even if serological responses wane, a single dose of the Pfizer-BioNTech vaccine is associated with an antibody response indicative of immunological memory."
The study "Longitudinal protection following natural SARS-CoV-2 infection and early vaccine responses: insights from a cohort of community-based dental health care professionals" is available as a preprint on the medRxiv* server, while the article undergoes peer review.
SARS-CoV-2 is an occupational hazard for the dental profession
Dental care professionals are at high risk of being exposed to SARS-CoV-2 from patients' close distance and the non-use of face masks during dental appointments.
In June 202, the researchers recruited 1,507 dental care professionals from the United Kingdom to participate in the study. Participants provided a venous blood sample for serological analysis. Specifically, they measured the number of antibodies against the SARS-CoV-2 spike protein for 3 months and later, 6 months, with the observation period ending January/February 2021.
After the first wave of the COVID-19 pandemic, 16.3% of dental care professionals had antibodies — which is higher than the average 6-7% observed in the general population.
Natural immunity was observed in more minority populations. About 35% of Black dental care professionals had antibodies compared to the 18.8% and 14.3% observed in Asian and White dental care professionals, respectively.
The risk of exposure from SARS-CoV-2 appeared to be the same across all dental professions. Although receptionists, who do not have direct patient contact, had the lowest antibody levels at 6.3%.
Participants who smoked showed lower antibody levels (7.6%) compared to participants who never smoked (16.4%) and ex-smokers (17.6%).
Persistent antibody response after 3 months
Researchers took blood samples for serological analysis after a 3-month follow-up. Results showed 73% of participants continued to have antibodies against the coronavirus spike protein at 3 months.
The researchers also observed 42% of participants had anti-spike glycoprotein immunoglobulin G (IgG), and 16% had Immunoglobulin A (IgA) responses at the start of the study. After 3 months, responses decreased to 37% and 9%, respectively. Although, this result may be due to the procedural methods conducted by the team.
"The discordance between seropositivity defined by the detection of the total antibody response (IgGAM) against the SARS-CoV-2 spike glycoprotein, compared to the IgG isotype, arises from the optimization of the assay for seroepidemiological studies."
Natural immunity observed after 6 months
A 6-month follow-up was then conducted with a small group of 79 participants. Approximately 72% of participants continued to have antibody levels.
The risk of reinfection was lower for participants with antibodies. They showed a 2.8% risk for future infection than the 9.6% observed in participants who did not have antibodies at the start of the study.
The researchers write:
"As seropositivity at baseline in June 2020 could only be accounted for by SARS-CoV-2 infection, 198 these data suggest that the emergence of antibodies following natural infection with SARS CoV-2 is associated with a 74% risk reduction for future infection."
The researchers next looked at the amount of SARS-CoV-2 antibodies needed to prevent reinfection.
Based on the World Health Organization's standard for SARS-CoV-2 immunoglobulin and the baseline samples, the team estimated that IgG antibodies at 147.6 IU/ml were the minimum amount needed for 6-month protection from SARS-CoV-2.
Vaccination helps with antibody response from natural immunity
A total of 873 participants volunteered their blood samples after natural infection and vaccination. About 51.5% of participants received the first dose of the Pfizer-BioNTech vaccine.
"Vaccination on the background of prior exposure to the virus was associated with a more rapid and quantitatively greater total antibody response against the SARS-CoV-2 spike glycoprotein, consistent with the boosting of immunological memory."
Results showed a 49.1% increase in the antibody response. Participants who were never exposed to SARS-CoV-2 and had received the first vaccine dose showed a 95% antibody response 12 days after vaccination.
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.