Antibodies seem to be the key.22 Sep 2020 15:40
Studies regarding SARS-CoV antibodies and immunity:
- 17 of the 18 patients had shown neutralising antibodies by day 720 although at low levels.
- 6 patients who had been infected with a coronavirus were subject to it again 1 year later 33% had zero experience of illness those who did (67%) deployed 0% respiratory illness symptoms and the virus lasted on average 2 days against 5.6 days in the initial challenge.
Ties in with current thinking on Covid-19 in that there’s full immunity for circa 6months and very likely longer. Then as antibodies wane there’s still strong protection with the virus being far less potent.
“We found few studies that analyzed changes in antibody kinetics over the course of many years after illness onset42,43. The 18 SARS-CoV patients in Mo et al.23 were followed for 2 years; in that study, after peaking, IgM levels were undetectable by day 180. On the other hand, levels of IgG were still high on day 180 and gradually declined to still detectable levels by day 720, while neutralizing antibodies were detectable in 17 of 18 patients at day 720, but at low titers23. Cao et al.43 described similar long-term dynamics for IgG and neutralizing antibodies over the course of a 3-year study on SARS-CoV: titers for both peaked at month 4, and while they waned thereafter, 74.2% and 83.9% of patients had detectable levels of IgG and neutralizing antibodies, respectively, at month 36. Liu et al.47 found that a high proportion of 19 recovered SARS-CoV patients were positive up to 2 years post infection, with the percentage declining in the third year, a pattern similar to that found by Wu et al.49 in 18 patients50.”
“Most longer-term studies (>10 weeks) were for MERS-CoV and reported IgG and neutralizing antibodies; these showed the presence of IgG and neutralizing antibodies up to 60 weeks after symptom onset“
“Several studies exposed volunteers to two viral challenges, some months apart. Reed 9 rechallenged six volunteers who had been experimentally infected with HCoV-229E 8–12 months previously9. On the first challenge, all six developed symptoms and detectable viruses, and five of six experienced a significant rise in titer. In the second, zero of six experienced illness, detectable virus or significant rise in titer. Callow et al.8 rechallenged volunteers with the same dose of HCoV-229E, 1 year apart. Of nine volunteers who were infected in the first exposure, 6 (67%) were infected in the second exposure. However, none of these individuals developed respiratory illness symptoms and they experienced a mean duration of detectable virus of 2 days compared to a mean of 5.6 in the initial challenge.”
Ties in nicely with the updated government guidance and SAGE report. Need those machines going 24/7!
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