We’ve had a few of these stories in the headlines recently but I wanted to highlight two of them here. It appears that what we all hoped would be the case, i.e. that most people who get the virus will recover and thereafter retain a long term immunity to reinfection, is not going to work out. A Chinese study published in Nature last week suggests that antibodies to the virus may only last for a few months.
Antibodies — protective proteins made in response to an infection — may last only two to three months, especially in people who never showed symptoms while they were infected.
The conclusion does not necessarily mean that these people can be infected a second time, several experts cautioned. Even low levels of powerful neutralizing antibodies may still be protective, as are the immune system’s T cells and B cells.
But the results offer a strong note of caution against the idea of “immunity certificates” for people who have recovered from the illness, the authors suggested…
Antibodies to other coronaviruses, including those that cause SARS and MERS, are thought to last about a year. Scientists had hoped that antibodies to the new virus might last at least as long.
Today Fox News published a story in which a Columbia University infectious disease specialist reacts to the Chinese study:
“When you get an antibody test, we don’t really know enough to be able to assure you that you’re safe. And I think the more we’re learning about antibodies, the more we’re beginning to say we’re not so sure that you’re safe,” Dr. Daniel Griffin, an infectious disease specialist at Columbia University Medical Center, told Fox News…
“Many of us were quite disturbed when we saw this study out of China, which actually demonstrated that in a number of individuals, particularly these individuals with more mild disease, that we’re worried are the silent spreaders, that these individuals were losing their antibodies shield after just a month or two,” Griffin said.
As the Times’ story suggested, even low levels of certain antibodies may be protective, but a second study published by Nature specifically stated that plasma collected from most people recovering from the virus did not have enough of those antibodies to be strongly protected: “most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity.” The abstract continued, “Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.”
There’s a good video explaining this second study here. The bottom line is that as many as a third of people recovering from the virus didn’t seem to have enough antibodies to make them immune from subsequent infection. But it appears that the sicker people were, the more antibodies they had. So seriously ill patients may have much more resistance than those who had minimal symptoms. Also, the researchers identified a few specific antibody proteins that were highly effective at blocking the virus. This suggests it should be possible to design a vaccine that specifically generates these highly effective antibodies and thus give people greater immunity.
So it’s not all bad news but in combination these two studies seem to suggest that people who’ve had mild cases of the coronavirus may not have much protection or may not have it for long. It’s one more bit of evidence suggesting this really isn’t going to be over anytime soon unless we can come up with an effective vaccine.