The largest study to date on the virulence of the delta variant of the coronavirus offers worrying data, especially for the millions of people in the developing world who have not yet received a single dose of vaccine.
The work focuses on more than 43,000 people infected with coronavirus in England. The mean age of the population studied is 31 years. 80% were infected with the alpha variant, originally detected in the United Kingdom, and the other 20% with the delta, registered for the first time in India and which today is the dominant one in Spain and many other countries.
74% of all participants were not vaccinated
74% of all participants were not vaccinated and another 24% had received only one dose. That is why this work does not serve to understand the current situation in countries like Spain where the delta variant is dominant, but the vast majority of the population at high risk of covid is completely immunized.
The results of this study, published today in the medical journal The Lancet, show that those infected with delta had twice the risk of being hospitalized for covid than those with alpha.
Gavin Dabrera, a doctor from the UK Public Health Agency and co-author of the study, highlights that the vast majority of the participants were not vaccinated and that is essential to understand the results well. The work was carried out between March 29 and May 23 of this year. “We now know that vaccines provide excellent protection against the delta variant, which in the United Kingdom already accounts for 98% of all registered cases,” explains Dabrera in a press release. “It is vital that all those who have not yet received the complete vaccine have it as soon as possible,” he adds.
The delta variant of the coronavirus was first detected in October 2020 in India. Since then this version of the virus has spread throughout the world and has become the dominant one, thus defeating the alpha, or British, variant. Alpha was already 90% more contagious than previous versions of the pathogen, and a UK study also associated it with 58% higher mortality. In any case, this last data has not been confirmed in other countries.
The delta variant has at least three mutations that make it potentially more dangerous. Several studies found that this form of SARS-Cov-2 was 50% more contagious than the alpha variant. A preliminary study in Scotland suggested that the delta doubled the risk of hospitalization, a finding now confirmed by work in England. The Scottish study determined the variant present in each patient using a PCR, while the current one has used the complete sequencing of the virus genome, a much more reliable method.
In the current study, one in 50 patients was hospitalized. The medical team took into account several factors that aggravate the covid such as age, race and vaccination. After adjusting these and other indicators, they saw that the delta increased the risk of income 2.26 times compared to the alpha.
Vaccines may be significantly less efficient in preventing infections with the delta variant, but they continue to block severe covid and death
There are so few vaccinated in this study, 2%, that the results do not serve to show whether the delta variant increases the severity of the disease and the number of admissions among those vaccinated. Most of the studies published to date show that this is not the case: vaccines may be significantly less efficient in preventing delta infections, but they are still effective in preventing severe COVID and death.
“Any outbreak with the delta variant among unvaccinated people will place a greater burden on hospital services,” summarizes Anne Presanis, statistician from the UK Medical Council and co-author of the work. The vaccine drastically reduces the chances that someone infected with delta will suffer illness, need hospitalization or die, he says.
The study authors acknowledge some limitations in their work. A very important one is that the previous illnesses of those hospitalized have not been taken into account, a key factor as it can complicate the infection.
“The most important message that this study leaves us is that the delta variant represents a risk only in those who are not vaccinated”, highlights Marcos López, president of the Spanish Society of Immunology. “Furthermore, this study is very much a slave to the moment in which it was done, when the delta was not yet dominant. For example, now in Spain more than 90% of the cases are delta and we are not seeing a higher rate of hospitalization or more seriousness ”, he highlights.