Wednesday , November 25 2020

COVID-19 primary vaccines and herd immunity

On the other hand, large pharmaceutical companies have announced promising results for developed COVID-19 vaccines. “Flock immunity” is a goal most countries want to achieve, but experts doubt that the first vaccines will soon have a significant impact, according to Mediafax.

The last few weeks have brought good news, at least about the most anticipated COVID-19 vaccines.

Pfizer is getting better and better. After announcing an efficacy rate of over 90% for the new coronavirus vaccine, the latest study from the Phase 3 study shows that the figures are even more promising. According to the company, the vaccine is 95% effective in preventing infections, even in the elderly.

Modern says its vaccine is nearly 95% effective in preventing COVID-19, and the results of Oxford / AstraZeneca are expected next time.

We will probably have a vaccine approved in the coming months. But what will be the immediate effect on the spread of the SARS-CoV-2 virus? Although many hope to facilitate the so-called “herd immunity,” experts are quite skeptical.

To develop a theory in this regard, Reuters reported that we must first find answers to other questions: What is the rate of spread of the virus that causes COVID-19 disease? Will the first vaccines in place be able to stop the transmission of the virus or simply not make people sick? How many people will agree to get vaccinated? Will vaccines give everyone the same protection? And the list goes on.

“Sometimes collective immunity is misinterpreted as personal protection,” says Josep Jansa, an expert in health training and response at the European Center for Disease Prevention and Control (ECDC).

“It’s not appropriate to believe that they won’t harm me because there is collective immunity,” he added. “Collective immunity refers to the protection of the community and not of each individual.”

The ECDC estimates the vaccine threshold at 67%. Meanwhile, 60-70% of the population acquiring immunity to the new coronavirus is being discussed in Germany. Chancellor Angela Merkel said this month that restrictions on the epidemic in Germany could be lifted.

Experts from the World Health Organization also provide between 65% and 70% coverage with COVID-19 vaccine to achieve a level of immunity in the herd.

“The purpose of herd immunity is to protect vulnerable people,” said Eleanor Riley, a professor of immunology and infectious diseases at the University of Edinburgh. “The idea is this: for example, if 98% of the population gets vaccinated, there will be so few viruses in the community that the remaining 2% will be protected. That’s the goal.”

Calculations made by public health professionals are based on the reproductive rate or R value of the virus responsible for COVID-19 disease. This value is, on average, a measure of the number of people infected by an infected person, with no restriction on the transmission of the pathogen under “normal” circumstances.

Under the hypothetical conditions of total vaccine efficacy, the immunity limit percentages of the vaccine are calculated by dividing 1 R by subtracting the result from 1 and then targeting it 100 times.

For example, immunity to highly contagious measles, with an R value of 12 or more, will only be valid if at least 92% or more of the people in a group are immune. For a strain of viruses damaged by seasonal flu, in which case R has a value of about 1.3, the threshold would be only 23%.

“The problem is that we still don’t know how fast the virus spreads without taking any action,” said Winfried Pickl, a professor of immunology at Vienna Medical University. He believes the value of R may be “closer to 4 to 2” because even with the restrictions the index is around 1.5.

Amesh Adalja, a scientist at the Johns Hopkins Center, has estimated that a realistic threshold in the United States would be 70%. However, the number may increase depending on the effectiveness of coronavirus vaccines.

Experts say another important factor is whether vaccines imposed by the authorities can interrupt the transmission of the virus.

According to the evidence so far, the first COVID-19 vaccines will at least stop the development of the disease in people who are already infected. However, the risk of contamination remains the same.

“While it provides excellent protection against disease, it will not prevent the circulation of the virus and the risk of not getting vaccinated,” says Penny Ward, King’s College of Pharmaceutical Medicine, London

Bodo Plachter, deputy director of the German Institute of Virology at Mainz University Hospital, says it can be difficult to completely block respiratory infections with vaccines: himself. But it would be a mistake to think that the vaccine itself can remove the pandemic.

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