Tuesday, February 23, 2021

Herd immunity does not prevent the spread of any new mutated: One dose of vaccine is enough?


Ali Awwad wrote in “Al-Akhbar”:

More than 200 million people around the world, according to the Bloomberg website, have undergone the Corona vaccine, less than three months after the start of the vaccination campaigns. The current production quantity of vaccines is insufficient, especially since each vaccination process requires two doses (with the exception of Johnson & Johnson) per person, which theoretically means the need for approximately 16 billion doses to vaccinate the entire world population. This is what will not happen according to the current year or the next year (some reports talk about the need for between 4 and 6 years). And to make matters worse, pharmaceutical companies find themselves in a race with variants of the virus, which have become a real threat that could bring the number of vaccinated people back to zero.

To the question that preoccupies the world’s population about which of the vaccines is the most appropriate, another question is added today about the possibility of extending the time period between the two doses of each vaccine to immunize the largest possible number, and is vaccination with one dose sufficient to prevent severe infection that requires hospitalization?

Canadian researchers Danuta Scuronsky of the British Columbia Center for Disease Control and Gaston de Ceres of the National Institute of Public Health in Quebec confirmed in an article published in the New England Journal of Medicine that the period of time can be extended. 21 days) between the two doses of the “Pfizer” vaccine, allowing the first dose to include the largest possible number of people. The researchers explained that the first dose recorded an effectiveness rate of 92.6%, based on documents submitted by Pfizer to the US Food and Drug Administration (FDA). Although there may be “uncertainty about the duration of protection with a single dose,” the administration of the second dose a month after the first dose “provides little additional benefit in the short term.”

Last week, the Lancet medical journal also published a study that included 7214 employees at a medical center, showing that the vaccine was 85% effective in preventing symptoms of Corona within 15 to 28 days of the first dose.
Despite experts warning that more research is needed, and Pfizer’s announcement that “changing the time interval between doses is something that has not been evaluated yet,” these results indicate that strong immunity is generated after one dose, and thus the second dose can be postponed to Beyond the three weeks specified by the company.

Britain recently announced that it is about to schedule the two doses of the “Pfizer” and “Oxford-AstraZeneca” vaccines, with a difference of 12 weeks between them, while it is expected that trials will begin to suffice with a single and final dose.

In principle, most of the vaccines obtained an emergency use permit based on clinical trials in which two doses of the vaccine were used, says researcher in bacteriology at the Lebanese University, Dr. Qassem Hamzah.
He added to “Al-Akhbar”: “It is medically recognized that one dose of any vaccine is beneficial … but definitely less than the two doses.” However, «it is not recommended to change the scheduling of doses locally without any scientific document from the producing company». Hamza pointed out that the voices calling for extending the period between the two doses were caused by poor production around the world and the need to immunize the largest possible number of people. And «the goal now is no longer to eradicate the virus, but to reduce the number of deaths and hospitalizations. This is what some countries think can be done with a single dose.

Meanwhile, the European Center for Disease Control and Prevention warned that “mutated versions against which vaccines may be less effective will likely continue to appear.” And drug groups were asked to work on new-generation vaccines that would be adapted to combat new mutated versions. This week, the European Union and the United States announced the establishment of programs aimed at strengthening the “sequencing” processes necessary to monitor the evolution of mutated copies and monitor new copies as they emerge.

Hamzah pointed out that the “Oxford – AstraZeneca” vaccine had decreased its effectiveness by up to 20 percent against the South African variant from Corona during experiments carried out by the company. The effectiveness of the Johnson & Johnson vaccine was reduced to 51 percent against the same mutated. But he pointed out that these results are not 100 percent accurate, since the experiment did not take into account the effectiveness of several immune cells other than antibodies such as T-cells, indicating that “even if the vaccines were less effective on the mutated copies, this is Does not mean that it will not be effective at all ».

He said that herd immunity is not necessarily the end of the road for the virus within any society. Any new mutant could develop immunity to a different version. He recalled what happened in Manaus, the capital of the Amazon state in the northern region of Brazil, where the number of injuries last spring reached 76% of its two million people. After it was believed that the residents of the capital created herd immunity, a mutated version of Corona (called the Brazilian mutant) returned to spread among the residents of Manaus and around the world at the end of last year.
He stressed the importance of determining the “sequencing” of the virus within any community, to better understand and monitor the spread of the epidemic, contain new mutants in their infancy and prevent them from spreading.





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