Thread by @kakape

“We provide evidence that Omicron BA.2 reinfections do occur shortly after BA.1 infections but are rare”

Interesting preprint from Denmark looking at 47 cases of BA.2 infections coming shortly after BA.1 infection.

.medrxiv.org/content/10.1101/2022.02.19.22271112v1.full.pdf

Of these 47 cases:
42 (89%) were not vaccinated,
3 (6%) were vaccinated twice,
2 (4%) had one vaccination.

For comparison: In Denmark on the whole:
81% are vaccinated twice and 62% have received the booster.

None were hospitalized or died in follow-up period.
"Detailed information of symptoms was obtained for 33 of the cases, whereof most of them reported symptoms during both infections … The distribution of reported symptoms did not differ markedly between the two infections"

Still find sentences like this absolutely staggering in so many ways:

"Between November 21, 2021, and February 11, 2022, a total number of ~1.8 million individuals (32% of the Danish population) tested positive for SARS-CoV-2 in Denmark by PCR."

"The reinfection rate appears to be low given the high number of positive SARS-CoV-2 tests during the study period but still highlights the need for continuous assessment of length of vaccine-induced and/or natural immunity"

Authors make 2 interesting points:
1. "Given the short time period between infections it could be reasonable to re-evaluate the definition by ECDC that requires two positive samples with more than 60 days apart in order to consider reinfection."

2. Most reinfections were in people below the age of 30 "and the majority of these cases were not vaccinated, further emphasizing the enhanced immunity obtained by the combination of vaccination and infection compared to infection induced immunity only."

Here is the link to the preprint (link in first tweet was incomplete)

medrxiv.org/content/10.110…