November 28, 2021

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Vaccines may be difficult to curb COVID-19

Vaccines may be difficult to curb COVID-19

 

Vaccines may be difficult to curb COVID-19. Harvard Public Health Professor: Vaccines may be difficult to curb the spread of COVID-19, COVAX plan faces challenges.

Vaccines may be difficult to curb COVID-19.

Right now, the COVID-19 epidemic has been raging for nearly a year. On December 2, the United Kingdom approved the emergency use of the COVID-19 vaccine jointly developed by Pfizer Pharmaceuticals Co., Ltd. of the United States and BioNTech of Germany, and the vaccination was initiated on December 8.

However, the British cannot spend a traditional Christmas holiday as in previous years: British Prime Minister Boris Johnson announced on December 19 that the United Kingdom will tighten epidemic prevention during Christmas due to the discovery of a faster-spreading mutant strain of the COVID-19 virus Measures to raise the level of epidemic prevention and control in the capital London and southeast England to a new fourth level. In addition, according to the World Health Organization’s European Regional Office on the 20th, confirmed cases related to this mutated new coronavirus have been found in at least three countries outside the UK.

Previously, people had hoped to achieve “herd immunity” through mass vaccination and thus defeat the epidemic. However, Ryan, executive director of the World Health Organization’s Health Emergency Program, warned against blindly optimistic after the vaccine is on the market. “Vaccines are not equal to zero cases of new coronavirus pneumonia.” He said frankly that although vaccines are an important part of the fight against new coronavirus pneumonia, the vaccine itself will not end the pandemic.

In the face of endless “accidents”, can vaccines really help us gain herd immunity? What important role will developing countries and poor countries play in achieving “herd immunity” globally? Can developed countries and wealthy countries and international organizations fulfill their previous promises to distribute vaccines fairly?

In this regard, the US National Academy of Sciences and Harvard University School of Public Health Professor Barry Bloom (Barry Bloom) and Harvard University School of Public Health associate professor of infectious disease epidemiology William Hanage (William Hanage) explored the above issues.

Vaccine efficacy will be the key to determining “herd immunity”

Barry Bloom and William Hanach both said,  “herd immunity” was not a pleasing word at first.

The reason is that at the beginning of the epidemic, the British put the concept of “herd immunity” under the spotlight for the first time, which caused great opposition. In March 2020, the UK, where the epidemic is on the rise, announced its “anti-epidemic” plan. Prime Minister Johnson announced at a press conference that the UK has moved from the first phase of “containment” to the second phase—“delay”. Its core strategy is to “not strictly guard against death, tolerate the slow progress of the epidemic, and expect that most people will be asymptomatic or have only mild symptoms after infection, so that the population of the country will be universally immunized to control the epidemic.” This statement triggered A huge controversy between academic circles and the people.

Hanaki was the first person to put forward professional but concise views on the major issues facing “herd immunity”. In an article published in the Guardian on March 15th, he pointed out that herd immunity must be based on the development of a new coronavirus vaccine, otherwise the resulting “smallest mortality rate” will be placed on a huge population. It is the “horrible number of deaths.” In addition, the “herd immunity” measures proposed by the United Kingdom at that time did not fully consider the second wave of the epidemic. He emphasized: “The vulnerable and vulnerable people should not be exposed to the virus now on the basis of a hypothetical future.”

Although the second wave of epidemics has indeed arrived, but vaccines have also been developed in record time, how do we talk about “herd immunity” again?

Hanach said that he prefers to call herd immunity (Herd Immunity) “Population Immunity” or “Community Protection.” Then he can also protect other people, because it means that those who are not immune and will be infected are protected.

Based on some of the most basic mathematical models, we can get a threshold of 50% to 60%, that is, as long as the proportion of the global population that is immune to the new coronavirus reaches this threshold, then the world may reach herd immunity.

However, the actual situation is always more complicated.

The official website of the US “Science News” magazine pointed out that if the vaccine is to play the greatest role in preventing the onset of new coronavirus pneumonia and controlling the spread of the new coronavirus, it is sufficient to vaccinate enough people to accurately reach the herd immunity threshold. However, if the vaccine is less effective, more people need to be vaccinated to address the potential gap in immunity between different populations.

Hanach said that given that the COVID-19 vaccine may still have many uncertainties such as efficacy to be investigated, we need more information about the vaccine to make a judgment.
Pfizer vaccines and Moderna vaccines that have obtained the U.S. Food and Drug Administration (FDA) Emergency Use Authorization (EUA), both of which use mRNA technology.

Hanach pointed out that because this technology is too new and has no commercial precedent, we still don’t know how effective this vaccine is in preventing viral infections. Even if individuals are protected by the vaccine and will not suffer from serious diseases, it may still be Being infected by the COVID-19 virus and continuing to spread the COVID-19 virus, “Although I suspect that this is rare, we still need to do some work to truly determine this.”

Can vaccinations slow down the spread of the virus while preventing people from getting sick? This issue is important because slowing the spread of the virus is a key factor in whether the economies of various countries can restart. A Bloomberg report on December 9 disclosed that although the vaccine jointly developed by the University of Oxford and AstraZeneca Pharmaceuticals can prevent the onset of new coronavirus pneumonia for most people who have been infected with the virus, it is blocking the spread of the new coronavirus. The capacity is limited.

The vaccine research and development team published a peer-reviewed study in the British medical journal The Lancet on December 8. The results showed that the Oxford-AstraZeneca vaccine can only reduce the spread of the new coronavirus by about 27%, which is far lower Because the vaccine is 70% effective in preventing the onset of new coronavirus pneumonia.

At the moment, we still don’t know how the approved Pfizer and Moderna vaccines will affect the spread of the new coronavirus. If these vaccines cannot effectively prevent the spread of the new coronavirus at all, herd immunity cannot be achieved through vaccination.

However, there is at least one piece of optimistic news: Wang Huaqing, chief expert and chief physician of the Chinese Center for Disease Control and Prevention’s immunization program, previously pointed out that in general, virus mutations will not affect the vaccine’s immune effect against the virus. Regarding whether there will be major changes in the later stage of the new coronavirus, relevant institutions and vaccine companies in various countries are still paying attention and studying.

Fair distribution of vaccines faces challenges

The official website of the US “Science News” magazine also mentioned in its article that even if the vaccine can indeed effectively reduce the spread of the COVID-19 virus, it still requires a fair distribution of vaccines to achieve herd immunity on a global scale. Given that the existing vaccines have high requirements for logistics support such as transportation and storage, this goal is still extremely challenging.

If people in poor or rural areas do not have access to vaccines, the outbreaks in these areas may persist. If the epidemics in these areas spread to other areas, stopping the COVID-19 pandemic may become empty talk.

According to the Associated Press report on December 15, Arnaud Bernaert, the World Economic Forum’s global health director, once stated that of the approximately 12 billion doses of vaccine expected to go offline next year, wealthy countries have already ordered about 9 billion of them. The COVAX global COVID-19 vaccine plan led by WHO has not yet received a sufficient dose of vaccine.

Bernat pointed out that COVAX may not be able to get enough vaccines until quite late. It is reported that the goal of the plan is to provide vaccines to participating economies from the first quarter of next year as soon as possible, and to provide at least 2 billion doses of vaccine to the world by the end of 2021.

Amanda Glassman, executive director of the Global Development Center, pointed out that there is no guarantee that these vaccines will work in poor countries. At the same time, these countries may lack sufficient funds to cover the cost of COVAX to provide vaccines.

Bloom also told me that it is even more regrettable that the large amount of funds promised by some major countries to support the operation of the program has not flowed into COVAX. In addition, because of fear that COVAX may eventually fail, some developing countries are also withdrawing from COVAX, trying to find other ways to obtain vaccines for their countries.

In early December, Palau, a Pacific island country, announced that it would abandon the COVAX program and instead hoped to obtain vaccines donated by the latter from the US. Other low-income and middle-income countries, including Malaysia, Peru, and Bangladesh, have also been looking for other ways, and recently signed alternative plans to obtain vaccines with some vaccine manufacturers.

Bloom pointed out that in sharp contrast, rich countries are still getting as many vaccine orders as possible. For example, Canada has purchased 200 million doses of vaccine for its 38 million people—more than five times the country’s population. , They are even starting to consider how to deal with the extra dose of vaccine that is ultimately left.

In a recording of WHO internal discussions obtained by the Associated Press, WHO vaccine director Katherine O’Brien said bluntly: “The call for global solidarity has basically failed.”

“We are at a critical moment. The new US government is about to come to power, but the United States is not in the COVAX plan. I am worried that COVAX’s plan to distribute vaccines across the world will fail.” Bloom said.

A report issued by the Global Alliance for Vaccines and Immunization (GAVI) pointed out last week that COVAX was “established in record time and must navigate in unknown territory” and that “the risk of COVAX failure is very high.”

Kate Elder, a vaccine policy adviser for Médecins Sans Frontières, said that now it is GAVI, WHO and other organizations that need to discuss how to increase vaccine production. In this regard, on December 12, Zhang Wenhong, director of the Department of Infectious Diseases, Huashan Hospital, Fudan University, China, issued a document saying that China still has a window of six months to one year to gradually pass vaccination, establishing the Chinese people’s immune advantage against the COVID-19 virus. In accordance with the global demand for vaccines, we will fulfill the obligations of major countries to help non-vaccine producing countries in the world gradually establish herd immunity supported by vaccines.

(source:sina)


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