Naturally acquired antibodies from COVID-19 last up to 20 months

The Journal of the American Medical Association recently published a study from the Department of Surgery, Johns Hopkins University School of Medicine, on February 3, 2022.

The research answered the question. How long do naturally acquired antibodies against the SARS-CoV-2 virus last? Specifically, they focused on antibodies against the receptor-binding domain (RBD) of the SARs-CoV-2, the virus that causes COVID-19.

The SARS-CoV-2 virus attaches to the ACE2 receptor of humans by its RBD. Antibodies against the RBD prevent the virus from entering the cells to cause infections. That is one of the ways natural immunity works.

The presence of anti-nucleocapsid antibodies was also checked to confirm a prior COVID-19. The nucleocapsid is the middle part of the SARS-CoV-2 virus. And is not included in the COVID shots (Pfizer, Moderna, and Johnson & Johnson) used in the US. People vaccinated people who never had COVID before will have no anti-nucleocapsid antibodies.

The study sent out an announcement via Twitter and Facebook to invite people who had never had COVID-19 before and were not vaccinated for COVID to have blood tests done. A total of 816 respondents had their blood tested between September 24, 2021, and November 5, 2021.

Participants had a mean age of 48.0 years, 421 (52%) were women, and 669 (82%) were White (Table). Fourteen percent reported routine mask use in public. Anti-RBD and anti-N antibody presence/absence were correlated (95%; Cohen κ=0.908).

The results are divided into (1) people who are sure they had COVID-19 before, (2) those who think they might have COVID before but were not tested for it before, and (3) those who believe they did not have COVID before.

Results:

Among 295 reported COVID-confirmed participants,

293 (99%) tested positive for anti-RBD antibodies (≥250 U/mL, 44%; ≥500 U/mL, 27%; ≥1000 U/mL, 15%).
A median of 8.7 (interquartile, IQR, 1.9-12.9; range, 0-20) months passed since the reported COVID-19 diagnosis.
The median anti-RBD level among those tested positive was 205 (IQR, 61-535) U/mL.
There was no evidence of an association between time after infection and antibody titer (0.8% increase [95% CI, –2.4% to 4.2%] per month, P = .62) (Figure below).

Among 275 reported COVID-unconfirmed participants

152 (55%) tested positive for anti-RBD antibodies (≥250 U/mL, 18%; ≥500 U/mL, 12%; ≥1000 U/mL, 6%). The median level among those who tested positive was 131 (IQR, 35-402) U/mL.

Among 246 reported no-COVID participants

11% tested positive for anti-RBD antibodies (≥250 U/mL, 2%; ≥500 U/mL, 2%; ≥1000 U/mL, 2%). The median level among those who tested positive was 82 (IQR, 19-172) U/mL.

The figure below sums up the statement from the study.

Anti-RBD levels were observed after a positive COVID-19 test result up to 20 months, extending previous 6-month durability data.

Source: Alejo et al. 2022. JAMA. Anti–receptor-binding domain (RBD) levels did not differ by months since COVID-19 diagnosis (0.8% increase [95% CI, –2.4% to 4.2%] per month, P = .62). Data markers indicate individual anti-RBD titers, solid orange curve with shaded area, linear regression with 95% confidence range.

The antibodies lasting for 20 months are based on the start of the pandemic and the study date. It may be longer.

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Related:

Reference:

Alejo JL, Mitchell J, Chang A, et al. Prevalence and Durability of SARS-CoV-2 Antibodies Among Unvaccinated US Adults by History of COVID-19. JAMA. Published online February 03, 2022. doi:10.1001/jama.2022.1393
Israel A, Shenhar Y, Green I, et al. Large-scale study of antibody titer decay following BNT162b2 mRNA vaccine or SARS-CoV-2 infection. Vaccines (Basel). 2021;10(1):64. doi:10.3390/vaccines10010064

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