Here's a recent study looking at the effectiveness of various immunity (prior infection, vaccination, vaccination + boosted, hybrid) against omicron.
There are a lot of ways to slice the data. I suspect the antivaxxers will assert that the study shows that vaccines are not effective. Although two doses of vaccine is not effective against
infection 6 months after the second shot, having some form of immunity (regardless of how it was obtained) is very effective against severe Covid-19.
Also, hybrid immunity was better (albeit modestly) than prior infection alone with regards to infection. Unvaccinated people considering the vaccine will have better immunity if they get jabbed regardless of whether or not they were previously infected (unvaxxed but previously infected people frequently assert that their immunity is better than immunity from vaccines, but this is a non-sequitur with regards to the choice to get vaccinated).
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Results
The effectiveness of previous infection alone against symptomatic BA.2 infection was 46.1% (95% confidence interval [CI], 39.5 to 51.9). The effectiveness of vaccination with two doses of BNT162b2 and no previous infection was negligible (−1.1%; 95% CI, −7.1 to 4.6), but nearly all persons had received their second dose more than 6 months earlier. The effectiveness of three doses of BNT162b2 and no previous infection was 52.2% (95% CI, 48.1 to 55.9). The effectiveness of previous infection and two doses of BNT162b2 was 55.1% (95% CI, 50.9 to 58.9), and the effectiveness of previous infection and three doses of BNT162b2 was 77.3% (95% CI, 72.4 to 81.4). Previous infection alone, BNT162b2 vaccination alone, and hybrid immunity all showed strong effectiveness (>70%) against severe, critical, or fatal Covid-19 due to BA.2 infection. Similar results were observed in analyses of effectiveness against BA.1 infection and of vaccination with mRNA-1273.
Conclusions
No discernable differences in protection against symptomatic BA.1 and BA.2 infection were seen with previous infection, vaccination, and hybrid immunity. Vaccination enhanced protection among persons who had had a previous infection. Hybrid immunity resulting from previous infection and recent booster vaccination conferred the strongest protection. (Funded by Weill Cornell Medicine–Qatar and others.)<<<
This article states that 90% or more of Americans may have some form of immunity. Hopefully it's high enough to reduce the more severe effects of future waves. But, who knows? This blasted virus has been unpredictable.
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Sixty percent infected—if that’s even accurate—actually isn’t the most relevant metric when it comes to forecasting how rough the road ahead might be. Vaccinations, too, can confer protection. And the fraction of Americans who have been infected
or vaccinated is probably
above 90 percent. But because immunity against infection and transmission ebbs over time,
more than 90 percent exposed doesn’t translate to
more than 90 percent “protected” against another viral encounter.<<<
With time and effort, we can build enough protection to blunt surges—but herd immunity remains out of reach.
www.theatlantic.com
The "above 90 percent" in the article above links to a CDC page that estimated the overall seroprevalence at 94.7% in December of 2021. Given the huge surge in new cases in early 2022, it seems reasonable to think that, by now, well over 95% probably have some immunity.
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The nationwide blood donor seroprevalence survey estimates the percentage of the U.S. population ages 16 and older that have developed antibodies against SARS-CoV-2, the virus that causes COVID-19, from vaccination or infection. This percentage is known as seroprevalence.<<<
CDC’s home for COVID-19 data. Visualizations, graphs, and data in one easy-to-use website.
covid.cdc.gov