It will soon be three years since the start of the global health crisis caused by the SARS-CoV-2 coronavirus and, during this time, we have learned (sometimes the hard way) that getting ahead of the coronavirus is decisive. Knowing when an increase in cases will occur, intuiting the danger of the dominant variant and, as far as possible, anticipating new waves are determining elements that end up saving lives.
In recent weeks, data has been collected and evidence has been accumulating indicating that “the northern hemisphere is on track for an increase in COVID-19 cases this fall and winter.” New strains of the immunoevasive Omicron variant, the relaxation of many of the security measures, decreased immunity… the loose pieces are beginning to come together and that is why, just a few days ago, Nature Magazine published an exhaustive review with the fundamental issues of a foreseeable new wave of COVID for the coming months.
Will there be a wave of COVID-19 this fall and winter?
Of course this is the most direct and obvious question… and the answer is yes, it is very likely that we will see an increase in cases, hospitalizations and deaths during the winter. In some US states this increase in cases is already beginning. Weekly data on UK infections has also documented a rise in COVID prevalence in its last two reports. Other European countries are also seeing a spike in cases, and hospitalizations of people who test positive for SARS-CoV-2 are rising rapidly, albeit from low levels.
However, the intensity of this new wave will depend on different factors that are not yet clear. The sudden increases caused by the BA.5 Ómicron variant in recent months could lead to greater immunity in the population. Therefore, if the booster vaccination campaigns are launched effectively and if new immunoevasive variants do not emerge, we could seeing only a moderate uptick in cases… which brings us to the next question.
What could be the intensity of this new wave?
According to initial estimates, this new autumn-winter wave will be similar in size to the previous waves caused by BA.5, at least in terms of the number of infections. Hospitalizations will depend on other factors and, as indicated in Nature, “it is likely that the population’s build-up of immunity (thanks to vaccination and previous infections) will keep admissions lower than previous waves of COVID-19.”
Fortunately, we are in a completely different situation than the winter waves of 2020 or 2021, but we still have to remember that “an increase in cases is still associated with an increase in hospitalizations and deaths”.
Are there new variants behind the increase in the number of cases?
Not yet. The most recent reports continue to show Omicron as the dominant variant. In Spain, for example, the sequencing of random samples indicates that the percentage of Ómicron is 100% and that the predominant lineages continue to be BA.5 and its derivatives (BA.3/BA.4/BA.2).
However, Ómicron is a double-edged sword since, although it is less serious in cases, it is also highly transmissible and has a greater immune escape capacity (immunoevasion) than previous variants. For this reason, SARS-CoV-2 observers are tracking a wide collection of new variants from different branches of the Omicron family tree, keeping a close eye on certain sub-lineages.
In the UK and Europe they have detected a rapid rise of BQ.1 (a descendant of BA.5 with several key changes). In India, the generation of the BA.2.75 variant that sparked a wave of infection several months ago is now overtaking all others and is already dominant in that populous country. The BA.2.3.20 variant (another offshoot of BA.2) is growing rapidly in Singapore and has appeared in Denmark and Australia. “I’m pretty sure that at least one of these variants, or a combination of them, will lead to a new wave of infection,” microbiologist Tom Wenseleers explains in Nature.
What about new vaccines and booster doses?
All the scientific evidence we have points to the fact that COVID vaccines, whether older or newer, “remain highly effective, especially in preventing serious illness, something that should be the primary focus of fall and winter booster schedules.” winter of the countries.
Booster doses, including the new bivalent vaccines specifically targeting Omicron lineages, offer protection against infection and even confer a certain degree of protection against infection from different variants. Vaccines tend to stimulate the production of neutralizing antibodies that better recognize the ancestral virus, on which the first vaccines were based, rather than Omicron, and therefore a second dose of these vaccines may be needed to generate high levels of neutralizing antibodies specific to Omicron.
Our best move right now would be to focus booster campaigns on people most at risk of serious illness, including older people and people with underlying health conditions, who stand to benefit most from the extra protection.