Is Omicron more deadly? How much protection does Vaccination provide? How important is the booster in avoiding death or hospitalization from Omicron?
These are some of the questions we can answer with data. However, we need 50,000 cases in a country with good age cohort, vaccination, and outcome tracking and about three weeks’ time to begin to draw conclusions.
Why do we need so many cases and so much time?
If we want to know how deadly Omicron is, it takes about three weeks on average from the time someone is infected with SARS-CoV-2 and death. In three weeks, about half the people who will die have died of COVID.
Delta currently kills at a rate of about 1.5% with a 21-day lagged Case Fatality Rate (CFR). That means, every 1,000 confirmed cases result in 15 COVID-19 deaths.
If Omicron is similar, 1.5% 21-day lagged CFR with 5,000 cases will produce 75 deaths. In the US, for example, we want to know if vaccination reduces deaths, we’d need to compare the 40% “not fully vaccinated,” 37% "fully vax, but no booster," and 23% “Vaccinated including booster.”
If there is no vaccinate protection the data would look something like this:
However, if 60 deaths are among unvaccinated, that tells us not having at least 2 doses doubles the risk of death. But, the situation is the unvaccinated are younger on average than vaccinated. So looking at the data for only 5,000 cases and 75 deaths doesn’t account for the age differences and understates the protection.
COVID kills more older people. We need to have enough data to look at cases and deaths by age cohort. Ten year increments, as reported by Israel is a helpful way to control for the age differences. Instead of 5,000 Omicron cases, we need at least 50,000 + 21 days before we can tell how much protection vaccines provide.
When we have 50,000 or more Omicron cases in a country with good age cohort, vaccination, and outcome tracking, we will start to have a clearer direction of Omicron’s influence on the pandemic outcomes. As we cross 50,000 cases in the US, we can also look at correlation with masks and other NPIs. With 50,000 confirmed cases, if 70% of deaths are among those 65+, the data will still be somewhat thin among younger age groups. Therefore, we will likely need more than 50,000 cases to have more confidence in the direction of Omicron.
To track how many cases by country, the CDC links to this site: https://www.gisaid.org/hcov19-variants/.
Brown University’s School of Public health dashboard, www.GlobalEpidemics.org will continue to update our forecast projections and risk scores according to the latest data.