A University of Birmingham-led study of over a thousand dental professionals has shown their increased occupational risk of SARS-CoV-2 infection during the first wave of the pandemic in the UK.
The observational cohort study, published in the Journal of Dental Research, involved 1,507 Midland dental care practitioners. Blood samples were taken from the cohort at the start of the study in June 2020 to measure their levels of antibodies against SARS-CoV-2, the virus that causes COVID-19.
The team found 16.3 per cent of study participants—which included dentists, dental nurses and dental hygienists—had SARS-CoV-2 antibodies, compared to just six per cent of the general population at the time.
Meanwhile the percentage of dental practice receptionists with SARS-CoV-2 antibodies—who had had no direct patient contact—was comparable to the general population, supporting the hypothesis that occupational risk arose from close exposure to patients.
The study found ethnicity was also a significant risk factor for infection, with a higher percentage of black and Asian participants having SARS-CoV-2 antibodies, compared to white participants.
Blood samples were taken from participants three months later, in September 2020, when dental practices in England had re-opened with enhanced PPE and infection control measures in place, and once again in January 2021, six months after the start of the study, during the second wave of the pandemic when healthcare workers were being vaccinated.
The results showed that of those who had previous COVID-19 infection, over 70 per cent continued to have SARS-CoV-2 antibodies both at three months and six months later, and they were at a 75 per cent reduced risk of re-infection with the virus.
The study also demonstrated the immunological impact of COVID-19 vaccination, with 97.7 per cent of those without previous infection developing an antibody response at least 12 days after their first Pfizer vaccine. In those with evidence of previous infection, the antibody response was more rapid and higher in magnitude after a single dose of the Pfizer vaccine.
Furthermore, none of the cohort with a level of SARS-CoV-2 antibodies greater than 147.6 IU/ml in their blood tested positive for COVID-19 throughout the six-month period from the first to the final blood tests.
“This is the first time the occupational risk of exposure to a potentially fatal respiratory virus has been studied in a large dental cohort,” co-author Professor Alex Richter said.
“It is important that we now progress our research to ensure we have an understanding of how people are protected from re-infection with COVID-19 following natural infection and vaccination.
“The nature and duration of immunity in these cohorts will be critical to understand as the COVID-19 pandemic progresses, particularly with respect to the efficacy of vaccination strategies—single-dose, multiple-doses, vaccine combinations—and in relation to novel viral variants of concern.”