An update on the spread of COVID-19, its continued evolution and vaccine options

The COVID-19 pandemic may seem to have stalled, but it's not over yet. After three years, however, it’s possible to take a step back to ponder the five major points that have prompted numerous questions and ongoing debate. 1) The pathogenicity of the virus All viruses evolve over time, including SARS-CoV-2. Many variants have been identified and are classified by the WHO as “variants of concern” (VOC) or “variants of interest” (VOI). These are the famous Alpha, Delta or more recently Omicron, which have dominated the news in 2021 and 2022, and are today considered “formerly worrying.” Since the beginning of 2022, the Omicron variant has dominated the world, with the BA.5 sublineage. The strength of the latter lies in its ability to escape the immune protection induced by a first infection (by BA.1, etc.) and/or a previous vaccination. It tends to be replaced by the XBB.1.5 sublineage, from the United States and classified VOI. Read: The info so far on autumn COVID-19 shots, from sea to sea to sea Variants whose name begins with the letter “X” are called recombinant, because they result from the genetic mixture of two previous variants—in this case between two sublines of BA.2 for XBB.1.5. Recombination is a means of evolution of the virus in the same way as a “simple” mutation, which corresponds to a genetic modification of the virus. Variants have long been characterized by their place of emergence. The typologies by Greek alphabet (VOC) and by compound alphabet (VOI) then replaced the initial stigmatizing geographical name (“English,” “Indian” variants, etc.). Although the places where new variants emerge are varied, their rapid spread on a global scale obscures this aspect. 2) The most vulnerable public The vulnerable and elderly are at greater risk of developing complications, comorbidities and severe forms of the disease. But Covid-19 can affect everyone, regardless of age or physical condition. International studies have shown that social determinants are also associated with an increased risk of infection and severe Covid. The work of the Île-de-France Regional Health Observatory (ORS) and INSEE has notably highlighted excess mortality in the poorest areas from April 2020, particularly marked in Seine-Saint- Denis. Although no causal link has yet been clearly established, correlations with environmental, urban, social and healthcare system factors are possible. Furthermore, certain factors associated with long Covid have been described, such as the initial severity or the number of symptoms present in the acute phase. However, healthy individuals can experience long Covid with symptoms such as fatigue, chest pain and headache, experienced months after recovery from the acute infection. Read: Injecting techs into vaccination workflow 3. Preventing spread of the virus The transmission of SARS-CoV-2 is largely linked to the “viral load,” or the quantity of virus present in the body of infected or sick people. It is generally either airborne (via droplets, aerosol) or by contact (direct or indirect). Applying physical distancing measures therefore helps reduce the risk of transmission. And because it is mainly airborne, regular ventilation of closed spaces (air renewal) and wearing a mask are also relevant to reduce the transmission of the virus. A recent review of the literature highlighted that long-distance transmission (>2m) of SARS-CoV-2 was possible in confined places such as restaurants and offices and that this was associated with inadequate ventilation of these spaces. 4. The benefit of masks Wearing a mask is one of the key measures to reduce the spread of SARS-CoV-2, and respiratory infections more broadly. Indeed, wearing a mask would reduce viral exposure if worn adequately (mainly with regard to the FFP2 mask). Several studies examining its impact on the epidemic dynamics of SARS-CoV-2 have struggled to conclude that there was a significant effect on the spread of the virus. However, the authors did note a large number of existing biases in the trials conducted and a relatively small number of people who followed the guidelines on wearing a mask. This could have affected the results of the studies. A review of the literature covering 172 studies concluded that masks were effective in preventing the transmission of respiratory viruses (SARS-CoV-2, SARS or MERS). 5. The impact of vaccines The development of several effective vaccines against SARS-CoV-2 was a major breakthrough in 2020. Never before has a vaccination campaign started so quickly after the identification of a new pathogen. Vaccination has had a significant impact on the evolution of the pandemic by reducing viral load, incidence (number of new cases of a disease for a given period and population), hospitalizations and deaths, therefore saving tens of millions of lives around the world. According to a study, vaccination would have prevented 15 million deaths between December 2020 and December 2021. These beneficial effects were mainly concentrated in high-income countries. In the vast majority of cases, side effects were minor. The most common are fever, headache and myalgia (muscle pain), which seem to be seen more with mRNA vaccines. The rare cases of myocarditis (13 cases per 1 million doses) are mainly observed with mRNA vaccines (Pfizer, Moderna). While cases of thrombosis (10 cases per 1 million doses) are observed with adenovirus vaccines (AstraZeneca and Janssen). Vaccination remained effective in cases of infection with the Omicron BA.4 and BA.5 subvariants, which still predominate to this day. The effectiveness of vaccination is highest in the first two months following the injection and then decreases by half after nine months. Hybrid immunity, obtained after vaccination and natural infection with SARS-CoV-2, confers more lasting protection, with the infection being able to elicit a more diversified immune response. More to come Although the pandemic appears to be contained, the infection figures are still fluctuating. SARS-CoV-2 therefore does not seem ready to disappear and the future evolution of the epidemic remains unpredictable. Many questions remain, and consequently, much work remains to be done. This article is republished from The Conversation under a Creative Commons license. Read the original article.

An update on the spread of COVID-19, its continued evolution and vaccine options

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