Thread by @vipintukur

The most burning 🔥 Questions right now:

Will #SARS2 continue to mutate to escape antibody protection? Do we need another booster? If so, what’s the next formula? For example, do we need an Omicron-specific vaccine?
1/

By the time an Omicron-specific vaccine is tested, we won’t have an Omicron wave anymore. So, is there still value in rolling it out? 2/

It all depends on how the SARS2 keep on evolving? The problem is it’s not following a fixed pattern. We know about evolutionary features of two viruses namely #flu and #measles. 3/

The new #flu vaccine formula is fairly predictable, because the virus mutates in a ladder-like pattern: there is one major lineage, and every few years, a new variant sweeps and the others go extinct. 4/

On the other end of the spectrum is #measles (B). While measles mutates, it does not mutate to escape immunity. It has a more balanced evolutionary tree 5/

#Measles There is no immune pressure that constantly pushes one mutation to outcompete another. So there is no ladder-like pattern. And, thankfully, our vaccines from the mid-1960s still work today. 6/

But the flu and measles are very different from #coronaviruses. To understand how SARS2 may change to escape immunity over time, we must look at other coronaviruses that have been circulating for decades. 7/

Take the case of this common cold #CoV229 that has been circulating since at least the 1960s. It has also evolved over time. The CoV229E is probably a good indicator of what’s to come with SARS2 because the viruses look fairly similar. 8/

#CoV229E mutated over time in a clear ladder-like pattern, just like the flu
Over time, mutations of CoV229E eroded antibody protection. In other words, people that were only infected by CoV229E in 1984 weren’t well protected today. 9/

This tells us that we should expect a ladder-like evolution of #SARS2 through which we could predict the next variant.
However, much to our surprise, this hasn’t happened. 10/

#SARS2 has thrown us for a loop, as the mutations haven’t evolved in a ladder-like fashion. The next variant hasn’t been coming from the last: Omicron didn’t come from Delta, and Delta didn’t come from Alpha. 11/

The fact that #SARS2 has lacked a pattern of evolution like other coronaviruses or the flu is incredibly puzzling. 12/

But, we haven’t had a lot of time for this pattern to play out. It’s only been 2 years and other evolutionary trees, like #CoV229E, also had 2-year time frames in which there were no ladder-like changes. 13/

Most experts expect the ladder-like pattern to arise with #SARS2 eventually. But because it hasn’t yet, we don’t know which direction SARS2 is heading. This makes proactively predicting the next booster formulas challenging and risky. 14/

Do we need another booster right now?
There are really two camps of thought right now:

1-There is not enough evidence that we need another booster. Boosters are working fantastically well against severe disease during the Omicron wave. 15/

2-Roll-out another booster vaccine. Just like what #Israel is doing. Israel already rolled out a second booster (not Omicron specific formula) among those aged 60+ years. 16/

Bottom Line:

It's tough to make predictions, especially about the future.” And #SARS2 is making it even more difficult with its random evolutionary patterns. 17/

journals.plos.org/plospathogens/…

Here is the link of @dr_kkjetelina blogpost 👇

yourlocalepidemiologist.substack.com/p/predicting-t…