Is COVID-19 becoming as “benign” as a flu?

Ever since the beginning of the pandemic, there have been many claims that COVID-19 is not dangerous and, in fact, it is almost like seasonal influenza.

Very little is being done in a “normal flu” year to stop it from spreading, perhaps except nudging the elderly and those at risk to vaccinate. By implication, any strict measures to stop the spread of COVID-19 are seen as unnecessary.

A graph is making rounds in the news, suggesting that COVID-19 and specifically Omicron is now having a similar impact to flu. I have looked at the mid-2020 graphs in my previous posts.

Thus, according to this analysis, it is only in the 60+ age bracket where COVID-19 is more deadly than flu. It is good news, but we need to be very careful in the interpretation. Two things need to be noted about this graph:

  • It represents an average Infected-Fatility Rate, so it does not tell us about individual risks, particularly for older and vulnerable (although the same is correct for the flu IFR);
  • It comes from a highly vaccinated population in a country with high prior immunity due to previous outbreaks.
  • The results (for the Case Fatality Rate) for other countries – like the US where the vaccination coverage is lower – are different and COVID-19 is still much more a problem.

On the values here: IFR uses serological data to estimate the “true” number of infected individuals while CFR uses the reported cases. The denominators (deaths) are the same in both cases, but IFR in England goes down to 0.1% while CFR is about 0.3%. Thus, we only report every 3rd case.

Assuming the same reporting efficiency, the IFR in the US would have been 0.25%-0.5% (CFR of 0.75%-1.5%, divided by 3); this is still 5-10 times as deadly as flu.

But there is more to these numbers:

Remember that the seasonal flu basic reproductive number – a measure of how infectious it is – is 1.2-1.4, going up to 1.3-2.0 for the 2009 strain and perhaps 2 for the 1918 strain. For comparison, for the “original” SARS-CoV-2 virus R was 2.4-3.4, going up to 4-5 for Alpha, 5.1 for Delta, and much higher for Omicron. S

So, there is a lot to celebrate as vaccination indeed appears to be working by dramatically blunting the deadliness of COVID-19. But it is also important to keep in mind that we are not yet completely safe.

Thanks to @jburnmurdoch