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NotAnotherEmpire t1_iraf0km wrote

The efficacy was heavily impacted by which variant was at issue. The two-dose vaccines remained highly effective against Delta even with waning. That was really, really good in the real world. Two dose wasn't effective against Omicron infection but the booster improved that.

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2796615

That Delta success is impressive as it didn't exist when the vaccines were developed and was a materially more severe threat.

Omicron is so different it likely wouldn't be classified as a "variant" if it and the original SARS-CoV-2 had been discovered outside a pandemic context.

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marr75 t1_iram7mu wrote

Depends on what you mean by effective. This article summarizes and links a few quality studies.

For symptomatic Omicron infections: 2 dose ~50-60% effective, 3-dose ~70-80% effective, 4-dose ~90% effective. The death rate was not reliably calculable in these studies because it was so low for all groups. So, is 50% efficacy against symptomatic infection, [some very high efficacy]% against death/severe illness "effective"? It certainly slows the spread and keeps a lot of people alive. Plus there's strong evidence you could "choose your own efficacy", if you were higher risk or just didn't want the hassle of symptomatic Covid, you could choose first and second boosters.

For reference, the flu vaccine, which is becoming a better comparison as we have vaccines against this family of coronavirii and they have become endemic (there's a smaller and smaller population with no prior immunity) is typically 40-60% effective against the most common strains of flu each year.

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