A new study has shown that the risk of being infected with the coronavirus is reduced considerably for up to 10 months following the first infection. 

The prospective VIVALDI study published in The Lancet Health Longevity evaluated over 2000 care staff (aged <65 years) and residents (>65 years age) at 100 long-term care facilities (LTCFs) in England between 1^st October 2020, and 1^st February 2021. The aim of the study was to see if there was an association between the baseline SARS-CoV-2 antibody status and subsequent infection in them. Blood samples were collected between June and November, 2020, at baseline, and 2 and 4 months thereafter and tested for IgG antibodies to SARS-CoV-2 nucleocapsid and spike proteins. 

Analysis of up to 10 months of data of follow-up from primary infection (assuming earliest infections occurred in March 2020) revealed the following key findings. 

• 33% of residents (n=226/682) had IgG antibodies to nucleocapsid gene at baseline compared to 29% of staff (n=408/1429).
• Both residents and staff who were antibody-negative at the start of the study were more likely to test positive on RT PCR than those who had antibodies at baseline.
• 20% of residents (n=93/456) who did not have antibodies at baseline tested positive for SARS-CoV-2 on RT PCR vs 2% (4/226) of residents who were antibody-positive at baseline.
• Likewise, 11% (n=111/1021) staff members who were antibody-negative at baseline had PCR-positive tests compared with 2% (n=10/408) of staff members who were antibody-positive staff at baseline.
• Residents who were previously infected had 85% less chances of reinfection, while vs 60% in staff members with previously infection had a 60% reduced risk of reinfection. 14 cases of possible reinfection were detected amongst those who had been previously infected, mostly among the staff members. Although 11 of these reinfection cases were symptomatic, none needed hospitalization. 

These observations are from LTCFs owned by one particular healthcare group. Data from other LTCFs are also now being analysed.

Based on their findings, the study authors concluded that although they were vulnerable to reinfection, the risk was considerably reduced among staff and residents who had IgG antibodies to nucleocapsid protein suggesting that the antibodies provides a high degree of protection against a second infection for up to 10 months. Also, only few reinfections were detected and those that occurred were not severe.

(Source: Krutikov M, et al. Incidence of SARS-CoV-2 infection according to baseline antibody status in staff and residents of 100 long-term care facilities (VIVALDI): a prospective cohort study. The Lancet Health Longevity. Published June, 2021)