The April 2020 variant has an R0 of about 2.5. The Herd Immunity Threshold is calculated as 1-1/R0. So for an R0 of 2.5, we have 1-1/2.5 or 0.6 (60%).
Since that time, the UK, South Africa, Brazil, and India variants have emerged. They're all present here. Some of them spread significantly more and thus have a higher R0. Recent estimates for the variants range from about 4.3 to 5.2. Plug that back into the HIT formula and you get 77% - 81%.
The virus is moving the goalposts through mutation. The math remains constant.
"take a vaccine that may or may not give me 6 months of protection, and likely will need a “booster”."
The vaccines available today were formulated against the original Wuhan SARS-CoV-2 virus. The April 2020 variant that took over worldwide (due to its significantly increased spread) had no changes to the S protein and thus is still very much covered by the vaccines. Certain variants (notably the South Africa and Brazil variants) have changes to their protein structures that enable them to partially evade immunity developed against the April 2020 variant or original Wuhan virus. P.1 (Brazil variant) is particularly bad about this. In a Brazilian city where 70% of the population had already been infected and recovered from COVID-19, P.1 showed up and tore through the city for a second round.
The vaccines elicit higher antibody levels than a mild or asymptomatic COVID-19 infection. So unless you've had a severe COVID-19 infection, the vaccines provide more protection. However, that protection is imperfect, particularly against variants like P.1. The "booster" coming in the fall specifically targets the variants to provide better protection against them. It's not because the immunity developed from getting vaccinated suddenly vanishes; it's to improve that immunity against variants with structural changes that make antibodies for the April 2020 variant less effective.
Can you provide sources for this?
Those are a whole bunch of wishy washy words. "a Brazilian city" "showed up" "tore through". Does "infected and recovered" mean "had symptoms, was diagnosed via positive PCR test and then symptoms resolved" or does it mean "PCR test discovered proteins in their nose"?
Are they claiming that a large number of patients who had Covid became re-infected with the variant or simply that the community was affected by 2 strands?
The former would be surprising since people who had SARSCoV-1 are immune to SARSCoV-2. SARSCoV-1 and SARSCoV-2 are genetically 20% different while the variants are about 2% genetically different from one another.
That’s was very well explained and brilliant.
Thanks.