Epidemiologists estimate over 160 million people worldwide have recovered from COVID-19. Those who have recovered have an astonishingly low frequency of repeat infection, disease, or death. That immunity from prior infection protects many people now where vaccines are not yet available.
(Article by Jeffrey Klausner, MD, MPH, and Noah Kojima, MD republished from MedPageToday.com)
Earlier this month the World Health Organization released a scientific update stating that most people who have recovered from COVID-19 develop a strong protective immune response. Importantly, they summarize that within 4 weeks of infection, 90% to 99% of people who recover from COVID-19 develop detectable neutralizing antibodies. Furthermore, they conclude — given the limited amount of time to observe cases — that the immune response remains strong for at least 6 to 8 months after infection.
This update echoes what the NIH reported in January 2021: The immune response of more than 95% of people who recovered from COVID-19 had durable memories of the virus up to 8 months after infection. The NIH went further to state that those findings “provide hope” that people who get vaccinated will develop similar lasting immunity.
So why are we so focused on vaccine-induced immunity — in our goals to reach herd immunity, our gatekeeping on travel, public or private events, or mask use — while ignoring natural immunity? Shouldn’t those who have natural immunity also be able to return to “normal” activities?
Numerous scientists have found that there is a decreased risk of re-infection and extremely low rates of hospitalization and death due to repeat infection. The range of reduction of re-infection from COVID-19 was between 82% to 95% among six studies that encompassed nearly 1 million people conducted in the U.S., the U.K., Denmark, Austria, Qatar, and among U.S. Marines. The study in Austria also found that the frequency of re-infection from COVID-19 caused hospitalization in only five out of 14,840 (0.03%) people and death in one out of 14,840 (0.01%).
In addition, newer U.S. data, released after the January NIH announcement, found protective antibodies lasting up to 10 months following infection.
As public health policymakers reduce the discussion of immunity to vaccination status, largely ignored are the complexities of the human immune system. There are multiple highly encouraging research reports showing that blood cells in our body, so called “B cells and T cells,” contribute to the cellular immunity after COVID-19. If SARS-CoV-2 immunity is similar to other severe coronavirus infections like SARS-CoV-1 immunity, that protection could last at least 17 years. However, tests to measure cellular immunity are complex and expensive, making them hard to get and preventing their use in routine medical practice or in public health surveys of the population.