BA.5 update for July 12, 2022
BA.5 now accounts for 65% of all sequenced cases of SARS-COV-2 in the US. BA.4 and BA.2.12.1 each account for 16-17%. The rest of the variants (original BA.2 and all the BA.1 lineage family) are on their way out or gone. BA.5 is the dominant variant nationwide.
🦠There have been a lot of viral tweets and Instagram posts suggesting that BA.2 has an R0 value of 18.6. This estimate originally came from a Guardian article on July 4. Taking a step back, the R0 value is the average number of transmissions that an infected person causes in a completely susceptible population. So it is only appropriate to estimate the R0 at the beginning of the epidemic. The "0" in R0 actually means "time zero". We also have nowhere near a completely susceptible population. We have about 78% of the population vaccinated, and a large serological survey estimates that over 57% of the population has had COVID-19. This Guardian piece used data from a preprint article which estimated the growth advantages of BA.4 and BA.5 (over BA.2) in South Africa, and they applied those growth advantages to an R0 value that they found for BA.2 (which is similarly methodologically inappropriate to report, for the reasons just discussed). Viral growth advantage arises from both increased transmissibility and immune escape from previous infection and vaccines. So it involves more than just the number of onward transmissions. So, this estimate of "R0=18.6" was not derived from a proper epidemiological analysis. The variant is definitely very transmissible however; I am not downplaying or disputing that fact.
🦠There continues to be immune escape for both vaccinated people and we do have people being reinfected with BA.5 that have had Omicron before. The vaccines are still protecting against severe disease. Per CDC data in April 2022, the primary series (2 shots) is associated with a 6x decreased risk of death in ages 5+. In ages 50+ those who were double boosted were 4x less likely to die of COVID-19 than those with only a single booster, and 42x less likely to die than an unvaccinated person of the same age group. So getting whatever booster that you are authorized to get is very important! There will be omicron specific boosters in the fall, probably October, but getting your booster now will not preclude you from also getting that vaccine.
🦠This morning the WHO held a press conference and verified that there is no data suggesting this variant BA.5 is more severe clinically than BA.2, however we do have an increase in hospitalizations, especially in the 70+ age group. A more transmissible variant means more cases, which unfortunately also means more severe cases.
🦠My recommendations as always are to ✅layer mitigations: ✅wear a mask KN 95 / N95, ✅test before gathering with others, ✅outside is better than inside for ventilation, ✅get boosted.
❤️Be careful out there! ❤️
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