The British variant is about 45% more contagious than the original strain of the coronavirus, according to Tel Aviv University researchers.
Their study was conducted using the results of some 300,000 PCR tests collected from December 6 to February 10 from the laboratory established by TAU in cooperation with the Electra Company in March 2020. The findings were published in the online journal Cell Reports Medicine on Sunday.
While most virus mutations are inconsequential, a variant is generated when several mutations cluster together and the virus creates a different protein. In the case of the coronavirus, the key protein is the spike protein, which is found on the surface of the virus and allows it to penetrate host cells and cause infections.
“We use a kit that tests for three different viral genes,” TAU Prof. Ariel Munitz said in a press release. “In the British variant, also known as B.1.1.7, one of these genes, the S gene, has been erased by the mutation. Consequently, we were able to track the spread of the variant even without genetic sequencing.”
The British variant spread fast in Israel as the vaccination campaign was getting underway at the end of December. An expected significant improvement in the morbidity rate due to the vaccines was delayed because of the variant, experts have said.
The PCR results showed that the variant was responsible for 5% of Israeli coronavirus cases identified in the lab on December 24. About six weeks later, it was the cause of more than 90%.
“To explain this dramatic increase, we compared the R number of the SARS-CoV-2 virus with the R of the British variant,” said Munitz, the lead author of the study together with TAU Prof. Moti Gerlitz. “In other words, we posed the question: How many people, on the average, contract the disease from every person who has either variant? We found that the British variant is 45% – almost 1.5 times – more contagious.”
The researchers considered the trend in positive cases in different age groups and found further proof of the efficacy of the vaccine.
“Until January, we saw a linear dependence of almost 100% between the different age groups in new cases per 1,000 people,” said TAU’s Dr. Dan Yamin, who participated in the study. “Two weeks after 50% of the 60+ population received the first dose of the vaccine, this graph broke sharply and significantly.”
“During January, a dramatic drop was observed in the number of new cases in the 60+ group, alongside a continued rise in the rest of the population,” he said. “Simply put, since more than 90% of those who died from COVID-19 were over 60, we can say that the vaccine saved hundreds of lives – even in the short run.”
The researchers found that positive tests on 60+ residents of retirement homes generally presented a lower viral load compared with 60+ persons in the general population.
“Since the residents of retirement homes are tested routinely, while other people are usually tested only when they don’t feel well or have been in contact with someone who had tested positive for the virus, we conclude that constant monitoring of at-risk populations is a method that works,” Munitz said.
“It is important to emphasize: The relatively low viral load was found in retirement homes despite the fact that the British variant had already begun to spread in all populations,” he said. “Consequently, we show that monitoring retirement homes, together with vaccination that gives precedence to vulnerable populations, prevent illness and mortality.”