Thread by @lgraca

Happy to share our 1st publication of 2023! Hybrid immunity (protection against Omicron BA.5 infection acquired by vaccination + Omicron BA.1/BA.2 infection) is stable over 8 months. Data from the 🇵🇹registry.🧵1/12
thelancet.com/journals/lanin…
@IMMolecular @lgraca @TheLancetInfDis

We previously showed that BA.1/BA.2 infection in a highly vaccinated population (Portugal) provides substantial protection against subsequent omicron BA.5 infection: nejm.org/doi/full/10.10… Similar results reported in Denmark and Qatar. What about the waning of protection? 2/12

We now address stability of the added protection conferred by infection of a vaccinated person (hybrid immunity). Using SARS-CoV-2 genetic surveillance data (great work from @irj_pt and J.P. Gomes), we defined periods when BA.1/BA.2 and BA.5 were dominant (>90% of isolates).3/12

We extracted from the Portuguese COVID-19 registry (SINAVE) the date of all infections reported in the country. SINAVE is very comprehensive, and until recently, there was a great testing effort in the country. Kudos to @DGSaude for maintaining the registry. 4/12

Then we split the BA.1/BA.2 and the BA.5 dominance periods into time slots of two weeks. Now, we could calculate the risk of people being infected with BA.5 in a given 2-week period, when they had a first infection by BA.1/BA.2 in different time slots in the past. 5/12

We found that the risk of BA.5 infection is initially very low (at 3 months), increases relatively fast between 3 and 5 months, and then stabilizes up to 8 months. At 8 months, hybrid immunity confers higher protection against infection than vaccination alone. 6/12

It is like a prospective study (in each BA.5 interval): recruitment of groups with different infection history (no randomization as the whole population is included!). All followed-up under the same conditions in each two-week interval when BA.5 infections were recorded. 7/12

We followed a similar approach (with shorter follow-up times) comparing hybrid immunity acquired following different combinations of Delta and Omicron BA.1/BA.2 infection (released as a pre-print). medrxiv.org/content/10.110… . 8/12

In conclusion, there are now in Portugal more people with hybrid immunity (vaccine+infection) than vaccinated people who were never infected… 9/12

…Our study shows that the high circulation of Omicron subvariants, in concert with high vaccination coverage, is contributing to a robust state of protection against challenges with new SARS-CoV-2 viruses. 10/12

Follow the recommendation of health authorities regarding vaccination. #vaccinessavelives and boosters save lives as well. See this nice study from our colleagues: medrxiv.org/content/10.110…. @andre_peralta 11/12

This work was a collaboration with @Tobi_grr Ruy Ribeiro, @VlterRFonseca1 Eugénia Fernandes, Pedro P Leite, Pedro Casaca, Carlos Antunes. The last praise goes to the PhD student that dealt with the tables and scripts @jtmalato 12/12
@IMMolecular @medicina_lisboa @FC_UL @DGSaude