There is increasing evidence that the Northern Hemisphere will see a significant increase in COVID-19-related cases this fall and winter. Scientists believe that new immune-evading strains, behavior changes and weakening immunity could lead to large numbers of COVID-19 cases in many countries.
Nature examines the factors that could drive a COVID-19 surge -- and what countries can do in order to mitigate the impact of the new generation vaccines that target Omicron.
Will There A Covid-19 Wave This Autumn And Winter?
The COVID-19 Scenario Modeling hub, a collaborative effort, presented several scenarios for the United States in mid-August. The models suggested that the United States could experience a relatively calm COVID-19 season after the surges due to the BA.5 Omicron variation -- which resulted in high immunity among the population -- as long as vaccine booster campaigns started quickly and no new variants weren't developed. A big increase in cases was not likely even with the new variant.
Justin Lessler, an infectious disease epidemiologist at UNC Chapel Hill, who is leading the modelling effort, said that hospitalizations have declined in line with projections more than a month later. There are other factors that could cause problems. Lessler says that the rollout of boosters, which target both Omicron and the original SARS virus-CoV-2 strain, has been slow. There are subtle signs that Omicron may be evolving and producing new immunity-dodging variants. Lessler says, "It could cause some upswings in the fall and winter months." According to Jennifer Nuzzo, an epidemiologist at Brown University in Providence (Rhode Island), some states in the United States are already seeing an increase in cases.
In the United Kingdom, the weekly SARS-CoV-2 infection survey, which is a gold standard for COVID-19 data, showed an increase in COVID-19 incidence in England and Wales over its previous two reports. Although it is still low, the number of people who have been diagnosed with SARS-CoV-2 in Britain and Europe is increasing rapidly.
Researchers believe that a variety of immune-dodging options are being developed globally. These will fuel an autumn-winter surge.
New Variants Are Behind Increasing Case Numbers
Tom Wenseleers (an evolutionary biologist at the Catholic University of Leuven, Belgium) says that it is unlikely. SARS-CoV-2 infection is on the rise due to a decline in immunity from previous infections or vaccines. People are also mixing more in this pandemic than ever before. Health officials say that social dynamics have almost returned to pre-pandemic levels in many countries, including the United Kingdom. Other respiratory viruses can thrive in cooler months, which could be due to extra indoor time.
Is There A New Omicron Strain In The Pipeline For This Fall?
Three or more of these mutations could be seen. We might see three or more of the Omicron sub variants driving past waves -- BA.2, B.4 and Ba.5 -- are receding, but their descendants seem to be gaining mutations that may help them spread.
SARS-CoV-2-watchers are monitoring an unprecedented number of variants from many branches of the Omicron family, according to Tom Peacock (virologist at Imperial College London). These variants have different ancestries but many of the same mutations in the SARS-CoV-2 spike proteins (the part of virus that immune systems target). Peacock says, "Clearly there is an optimal way for a variation to look going into the season."
Researchers keep an eye on sublineages. For example, the rapid rise of BQ.1 in Europe and the United Kingdom is a result of several key changes to BA.5 (a descendant of BA.5). According to Rajesh Karyakarte (based in Pune), who coordinates SARS/CoV-2 genetic sequencing in Maharashtra, India's spawn of the BA.2.75 variation that caused an infected wave several months back is now outperforming all other spawn. His team sequenced samples in September and found that a subvariant named BA.2.75.2 was the most prevalent, followed closely by a relative. BA.2.3.20 is another BA.2 variant that is rapidly growing in Singapore and has been discovered in Australia and Denmark.
Wenseleers says that "I am fairly certain that at least one variant or combination of them will cause a new epidemic wave." Because they are all acting in a similar way, it doesn't matter which one becomes the next big thing.
Why Is This Variant On The Rise?
Two words: immune escape. Researchers are tracking multiple changes to the receptor binding domain of spike proteins. This is where potent antibodies can target the spike protein and block infection. Yunlong Richard Cao, an immunologist from Beijing's Peking University, believes that multiple viruses are developing the same spike mutations. This is a major advantage for the virus' spread.
Cao and his collaborators evaluated the ability of the new crop variants to evade neutralizing antibody from vaccination and previous infections with other variants in a September preprint . BQ.1.1, a member of the BQ.1 familia with an extra spike change, and BA.2.75.2 were found to be the most immune evasive. They could even dodge most neutralizing antibodies that are elicited from infection with BA.5. The study found that two anti-omicron drugs are still effective against BA.2 (and BA.5), but their effectiveness against emerging Omicron subvariants is likely to decrease. Similar conclusions were reached by another team, which included Peacock, about BA.2.75.2. Cao says that the degree of immune escape is incredible right now.
How Big Are The Autumn-Winter Waves?
Based on initial estimates, Wenseleers believes that the size of autumn-winter waves is similar to those seen in BA.5 surges. This includes infection numbers. It is difficult to predict the impact on hospitalizations. Researchers believe that the build-up in immunity to vaccinations and previous infections will keep admissions lower than it was during past COVID-19 waves. However, how low this effect will be is not known. Lessler says that while it is a different game than in 2020 or 2021 but a surge would still likely be associated with an increased number of deaths and hospitalizations.
Even a mild COVID-19 outbreak could cause problems for hospitals. They are already facing backlogs and other conditions that place a significant burden on winter health systems. Influenza, which has not registered in the Northern Hemisphere for the past two winters is expected to return with a vengeance this season. This could fuel fears of a twindemic' of COVID-19 and influenza. Lessler says that hospitals can become quite stressed in a bad flu season.
What Do You Think About The New Vaccines.
Some protection from infection with new variants is possible through boosters such as bivalent vaccines. Scientists warn that this protection may not last for long. Scientists believe that one part of bivalent vaccines is based upon an Omicron subvariant -- BA.1 for UK-approved vaccines, and BA.5 for the United States. There are signs the vaccines stimulate the production of neutralizing antibodies that best recognize Omicron. These antibodies also help to identify the ancestral virus upon which the original vaccines were built. Cao suggests that boosters may be required to produce high levels of Omicron-specific neutralizing antibodies.
All evidence indicates that COVID-19 vaccinations, old and new, are highly effective in preventing severe diseases. Nuzzo believes this should be the primary goal of winter and autumn booster programs. This means that booster campaigns should be targeted at those most at risk for severe disease, such as older people or people with underlying conditions. She says, "We must put a laser beam on the protection against severe illness."
0 Comments