Thread by @FLAHAULT

1/9 - “A surge in #COVID19 hospital admissions driven by the #BA5 of #Omicron, accompanied by the inability of vaccines to prevent reinfection, has prompted health policymakers to rethink their approach to boosters.”
ft.com/content/4f71ac…

2/9 - “Research into immune imprinting, whereby exposure to the virus via either infection or vaccination determines an individual’s level of protection, is now driving the debate over the make-up of #COVID19 vaccines.”

3/9 - “Immunologists say that, >2y into the pandemic, people have acquired very different types of immunity to the #SARSCoV2, depending on which strain or combination of strains they have been exposed to — leading to big diff in #COVID19 outcomes between indiv and countries.”

4/9 - “The effect is more nuanced than ‘more times you have it, less protection you get’,” said Altmann, Imperial Collg London. “It’s more helpful to consider it as progressive fine-tuning of a huge repertoire. Sometimes this will be beneficial for the next wave, sometimes not.”

5/9 - “Our first encounter with the spike antigen, either through infection or vaccination, shapes our subsequent pattern of immunity through immune imprinting.”

6/9 - “#Omicron infection has little or no beneficial effect of boosting any part of the immune system — antibodies, B-cells or T-cells — among people who had been imprinted with earlier #SARSCoV2 variants. #Omicron is an especially stealthy immune evader.”

7/9 - “Vaccines currently in use were designed to target the virus as it first emerged from Wuhan, >2y ago. They retain high protection against severe disease and hosp admissions but their efficacy against transmission and mild infection wanes quickly, especially agnst #Omicron.”

8/9 - “99% of secondary schoolchildren tested positive for Covid antibodies from natural infection [in England]. [Now] the vast majority of Covid cases are reinfections in people whose immune defences acquired from vaccines or earlier infections do not hold up against #BA4/#BA5.”

9/9 - “Moderna and BioNTech/Pfizer have submitted lab data showing that their latest versions, targeted at Omicron, produce a potent Ab response against #BA4/#BA5. But we remain uncertain whether they will be > effective than receiving another dose of the original Wuhan vaccine.”