Vaccination may be the surest way to boost immunity against SARS-CoV-2 infection, but it is not the only way. And that’s an important consideration as the world looks for ways to live, safely, with COVID-19.
A study published in early February by JAMA found that 99% of unvaccinated adults who reported a positive COVID-19 test result had detectable antibody levels approximately 8.7 months after their initial diagnosis. Of these, 15% had ≥1,000 U/mL of SARS-CoV-2 spike protein anti-receptor-binding domain (RBD) antibodies, while 27% had ≥500 U/mL and 44 % had ≥ 250 U/mL.
The median anti-RBD level among those who tested positive was 205 U/mL.
Based on the findings, the researchers recommend that governments consider moving away from the controversial concept of “vaccine passports” in favor of “immunity passports”.
“Nearly everyone with documented COVID-19 infection had antibodies, and those antibodies seem to persist for quite a long time,” study co-author Dorry Segev, MD, PhD, who is Marjory K. and Professor of Surgery Thomas Pozefsky at Johns Hopkins School of Medicine, professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health and associate vice chairman of the department of surgery at Johns Hopkins Hospital in Baltimore, recently told HealthDay News. “We really need to start incorporating natural immunity antibodies into the context of immunity assessment, moving from vaccine testing to immunity testing.”
Segev was on a trip and unable to respond to Contagion at the due date.
In addition to antibody levels among confirmed cases, 55% of participants “who believed they had COVID-19 but were never tested” tested positive for anti-RBD antibodies, with 6% having ≥1,000 U/mL , 12% having ≥ 500 U/mL, and 18% having ≥ 250 U/mL.
Finally, 11% of participants who believed they had not been infected with SARS-CoV-2 and who had never been tested for the virus had detectable levels of anti-RBD antibodies, although at levels far below those of confirmed cases and those who knew they were sick.
“There is certainly evidence that antibody levels correlate with … clinical protection, and the same caveats for natural immunity are there for vaccine immunity,” Segev told HealthDay News.
Whether or not that’s enough to get the world to explore what it calls “immunity checking” remains to be seen – and, if so, what it would look like, given that checking levels of antibodies would require routine monitoring.
But it is food for thought as political leaders and public health officials consider the way forward.