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Bad news for the herd immunity strategists
https://www.ctvnews.ca/health/coronavirus/covid-19-immunity-might-not-last-long-for-asymptomatic-carriers-study-1.4995246
The study found that levels of antibodies were “significantly higher” in the symptomatic group during the acute phase, meaning the phase in which the virus is still present in the body. The researchers also noted that among the 37 asymptomatic patients, 21 developed damage in at least one lung, even though they exhibited no outward symptoms of the virus. The other 16 patients did not have any abnormalities.
Eight weeks after the patients left the hospital, researchers followed up with both groups and found the IgG levels in more than 90 per cent of symptomatic and asymptomatic patients had declined, with the median percentage decrease in both groups at more than 70 per cent. Additionally, 40 per cent of asymptomatic patients and 13 per cent of symptomatic patients had tested negative for the IgG antibody.
These declines are in contrast to similar research concerning the SARS and MERS outbreaks, which indicated that antibodies for these viruses can last more than two years and at least 34 months, respectively. This latest research could explain why some people have reported contracting the virus more than once.
Also problematic for the tragically slow antibody studies that are now taking place.
“Additional longitudinal serological studies profiling more symptomatic and asymptomatic individuals are urgently needed to determine the duration of antibody-mediated immunity.” The researchers also indicate that because the antibodies can decline quickly, that this study shows further need for a “timely” large-scale study of antibodies in order to get a fuller understanding of how many people have been infected with the virus.
I guess my wife and I will never find out whether we already had Covid-19 in Februari. Not that it matters if we can get re-infected again anyway by now. And how long will vaccines be effective?
