2020 was the year of the Covid lockdowns, 2021 the year of vaccines and 2022 the year of the global reopening. 2023 will be the year of the variant prediction. The first variants of Covid concern to be identified, from Alpha in the UK to Beta in South Africa, clouded the picture of where the pandemic would go next. Alpha was inherently better at transmission, while Beta could evade pre-existing immunity to some degree. What would the long-term pattern of evolution look like?
The picture became clearer in 2022, with the Omicron BA.1 variant causing major epidemics. This led to a buildup of immunity within populations, followed by decreased transmission, only for a new subvariant, BA.2, to emerge against which this immunity was less effective. Large epidemics followed and the cycle started again, with another cycle in mid-2022 when BA.5 emerged.
If this evolutionary trajectory continues, we will see this cyclical pattern in 2023 and beyond. It is a dynamic similar to that of seasonal coronaviruses that have been causing epidemics for decades. A 2021 study by researchers at the Fred Hutchinson Cancer Research Center found that coronaviruses gradually evolve over time, making previous immunity less effective.
This will create a challenge for Covid-19 vaccination campaigns; If viruses evolve this way, we would ideally update vaccines so that the viral proteins in the vaccine more closely match what our bodies will find in circulating variants. But updating vaccines takes time. For influenza, the World Health Organization makes recommendations twice a year on which variants should be in that season’s vaccine in each hemisphere. Due to manufacturing and distribution timeframes, winter vaccination decisions are made more than six months in advance. That makes vaccine selection a predictive problem.
When it comes to selecting influenza vaccines, teams use a variety of data, from the growth rates of circulating variants in genomic data to evidence of their immunological properties. An additional complication is the variability in what different populations have previously been exposed to. Some countries may have more pre-existing immunity than others, and therefore variants that can evade this immunity have more advantages. We often see different influenza viruses dominating in different continents and countries.
In 2023, this prediction challenge will also become routine for Covid. Some countries have already approved injections that are adapted for the Omicron BA.1 sub-variant. But how well will these new vaccines match up with variants that will circulate later? Decisions for winter 2023-24 in the northern hemisphere will likely need to be made in early 2023. Making the right decision could have important implications for the size and severity of future waves of covid. For the H3N2 influenza subtype, which tends to cause the largest seasonal epidemics, challenges around vaccine selection and manufacturing mean that effectiveness against symptomatic disease is often less than 50 percent.
Down the road, there is hope for breakthroughs in “universal” coronavirus vaccines, which will be highly effective against a wide range of variants. But the history of the development of other universal vaccines, such as that for influenza, suggests that absolute success is far from guaranteed. As a result, next year will be the start of a long game of cat and mouse, pitting vaccine updates against an evolving virus. Solving this prediction question and rolling out the resulting vaccines will be one of the major health challenges of 2023.
Source: news.google.com