Study: COVID antibody may prevent reinfection for 6 months

In the UK, few healthcare workers who recovered from COVID-19 and had immunoglobulin G (IgG) antibodies against the virus were re-infected in the next 6 months. Research December 23 New England Journal of Medicine..

A prospective longitudinal cohort study measured the levels of IgG antibodies against the coronavirus spike protein and nucleocapsid in symptomatic and asymptomatic health care workers at Oxford University Hospital undergoing COVID-19 testing. The test started on March 27th and the follow-up ended on November 30th.

Screening confirmed that 11,364 staff members did not have antibodies to SARS-CoV-2, the virus that causes COVID-19, and 1,265 were antibody-positive. Eighty-eight of them were later negative.

Of the 223 workers who were negative for anti-spike antibodies and positive for COVID-19 in the initial screening, 100 were asymptomatic and 123 were symptomatic.

Similar reinfection rates for both antibody types

Of the 1,265 staff members who had antibodies, only two were positive for COVID-19 at baseline. Neither had any symptoms. However, after 160-199 days, three were positive for coronavirus infection, one with anti-spike IgG, one with anti-nucleocapsid IgG, and the other with both.

Workers with both antibodies were infected with the coronavirus prior to antibody testing. After five negative COVID-19 tests, the worker was positive once on day 190, but was asymptomatic, then negative, and had no elevated antibody levels. A fourth staff member with both types of antibodies was COVID-19 positive 231 days after the initial infection, but was negative on the next two tests. Subsequent antibody assays showed reduced levels of both types of antibodies.

Another 864 (68%) with antibodies remembered to have had symptoms characteristic of COVID-19 in the past, while 466 (37%) had previously had SARS-CoV-2 infection. It was confirmed (262 people with symptoms).

Of the 11,364 workers who did not have coronavirus antibodies, 24 (0.2%) were previously positive for infection, recalling that 2,860 (25%) had COVID-19 symptoms prior to screening (20%). The latter were all asymptomatic).

After adjusting for age, gender, screening month or calendar time as continuous variables, the incidence ratio of staff using anti-spiked antibody was 0.11 and COVID-19 positive results were inversely correlated with anti-spiked antibody testing. .. Whether they were above or below the positive threshold (P<0.001 for trends).

Similarly, of the 12,666 staff members for whom anti-nucleocapsid IgG was previously used as a marker for COVID-19 infection, 226 of the 11,543 non-antibody workers were positive for COVID-19. In contrast, 2 out of 1,172 workers with antibodies (adjusted incident rate) ratio, 0.11). However, the percentage of positive COVID-19 tests decreased with increasing levels of anti-nucleocapsid antibody titers (P<0.001 for trends).

Overall, 12,479 healthcare professionals had both anti-spike and anti-nucleocapsid antibodies at baseline. Of the 11,182 staff who were negative for both types of antibodies at baseline, 218 were later COVID-19 positive, while 1 in 1,021 were both positive (incidence ratio 0.06). , 2 out of 344 patients had mixed antibody test results (incidence). Ratio, 0.42).

Immunity needs further characterization

The authors found that the presence of anti-spiking antibodies was associated with a much lower risk of SARS-CoV-2 infection than follow-up, with only two COVID-19 reinfections in antibody-positive workers. It occurred and both were said to be asymptomatic. This suggests that previous infections that result in antibodies to SARS-CoV-2 are associated with protection from reinfection for at least 6 months for most people. “

Researchers cannot conclude whether the results or current levels of past positive antibodies determine immunity, or whether protection is provided by measured antibodies or unassessed T cell protection. Stated. They called for future research in children, the elderly, and people with underlying disorders such as immunosuppression.

“In this cohort and other cohorts, including the use of both humoral and cell-mediated immunity markers for SARS-CoV-2, assess the scale and duration of protection from reinfection, symptomatic disease, hospitalization or death. In order to do so, continuous follow-up is required. The protective effect against infection, “the authors write.