Antibody Status and Incidence of SARS-CoV-2 Infection in Health Care Workers. Sheila F. Lumley et al. N Engl J Med 2021; 384:533-540
BACKGROUND: The relationship between the presence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the risk of subsequent reinfection remains unclear.
METHODS: We investigated the incidence of SARS-CoV-2 infection confirmed by polymerase chain reaction (PCR) in seropositive and seronegative health care workers attending testing of asymptomatic and symptomatic staff at Oxford University Hospitals in the United Kingdom. Baseline antibody status was determined by anti-spike (primary analysis) and anti-nucleocapsid IgG assays, and staff members were followed for up to 31 weeks. We estimated the relative incidence of PCR-positive test results and new symptomatic infection according to antibody status, adjusting for age, participant-reported gender, and changes in incidence over time.
A total of 12,541 health care workers participated and had anti-spike IgG measured; 11,364 were followed up after negative antibody results and 1265 after positive results, including 88 in whom seroconversion occurred during follow-up. A total of 223 anti-spike–seronegative health care workers had a positive PCR test (1.09 per 10,000 days at risk), 100 during screening while they were asymptomatic and 123 while symptomatic, whereas 2 anti-spike–seropositive health care workers had a positive PCR test (0.13 per 10,000 days at risk), and both workers were asymptomatic when tested (adjusted incidence rate ratio, 0.11; 95% confidence interval, 0.03 to 0.44; P=0.002). There were no symptomatic infections in workers with anti-spike antibodies. Rate ratios were similar when the anti-nucleocapsid IgG assay was used alone or in combination with the anti-spike IgG assay to determine baseline status.
CONCLUSIONS: The presence of anti-spike or anti-nucleocapsid IgG antibodies was associated with a substantially reduced risk of SARS-CoV-2 reinfection in the ensuing 6 months. (Funded by the U.K. Government Department of Health and Social Care and others.)
You can read the conclusions. In terms of antibodies they can be protective against the effects of viral attack, or they can be sterilizing and stop you passing on the virus. Whilst there is some evidence that the latter can occur which is a reason why it is worth getting the vaccine to protect your fellow humans. However, it may not stop you getting infected and in that sense there is benefit to you as it will reduce your risk of hospitalisation and severe disease. I think vaccination is more likely to achieve the latter. There is evidence that vaccination reduces viral loads and that it takes a couple of weeks to occur tells us there is more to protection from the SARS-CoV-2 than the innate (macrophages). This takes about 2 weeks to develop. It is known that many people do not have a strong antibody response at 2 weeks so it is T cells or T cells and antibodies such as IgM produced early after infection. This study implicates that antibodies are important