March 21, 2023

Medical Trend

Medical News and Medical Resources

WHO: World will not achieve herd immunity for COVID-19 in 2021

WHO: World will not achieve herd immunity for COVID-19 in 2021


WHO expert: World will not achieve herd immunity for COVID-19 in 2021.  The latest statistics show that an average of 2.41 million COVID-19 vaccines are injected into people’s arms every day in the world. According to the transmission coefficient of the new coronavirus, herd immunity can only be established after about 70% to 80% of the population is vaccinated, and the spread of the virus will be blocked. In order to achieve this goal, a vaccination campaign of unprecedented scale is now being launched on a global scale.

In this regard, Zhang Wenhong, director of the Department of Infectious Diseases at Huashan Hospital of Fudan University, pointed out: The speed of vaccine advancement determines the future of the confrontation between humans and the COVID-19 epidemic. The faster the vaccination rate, the more effective the epidemic can be controlled, and the speed of virus mutation cannot keep up with the speed of disease prevention and control.

However, in this process, factors such as the protective efficacy, productivity, and willingness of vaccination of the COVID-19 vaccine will all affect the realization of the ultimate goal. According to estimates by an associate professor at the Yale School of Public Health in the United States, China needs close to 1 billion people to complete the vaccination to achieve the threshold of herd immunity. As of January 13, 2021, China has received about 10 million doses of the COVID-19 vaccine, but relative to the goal of 1 billion people, this is just the beginning. The vaccination in Europe, America and other countries is currently not as expected, and new challenges have emerged.


Vaccine effectiveness is not No.1 

Chinese vaccine makers are beginning to enter the harvest period. On December 31, 2020, it was officially announced that the COVID-19 inactivated vaccine of Sinopharm Beijing Institute of Biotechnology had been approved by the State Food and Drug Administration on the evening of December 30 for conditional listing. The results of the Phase III clinical trial showed that the vaccine has a protective efficacy of 79.34% against diseases caused by new coronavirus infection.

The vaccine of Sinopharm Beijing Institute is the fourth in the world to release the effectiveness data of Phase III clinical trials, followed by another inactivated COVID-19 vaccine from China. The vaccine manufacturer Kexing has carried out phase three clinical studies in Brazil, Indonesia, Turkey, and Chile, but Brazil has the largest number of participants in the trial, so its effective rate data will be more representative. However, the release of Coxing’s clinical trial results in Brazil has been delayed repeatedly, the first time was December 15, 2020, and the second time was December 23.

On January 12, Coxing’s Brazilian partner Institute of Butantan announced that Coxing’s vaccine protection rate was 50.4%, lower than the 78% announced a week ago. At the press conference, the person in charge explained that the 78% effective rate is based on the statistics of mild, moderate, and severe cases. If you include very mild cases (said to have symptoms but did not go to the doctor), the number is 50.4 %-167 cases of infection in the placebo group, 85 cases in the vaccine group. On January 17, local time, the Brazilian National Health Inspection Agency authorized the emergency use of the vaccine in Brazil.

Kexing responded to China News Weekly that all the subjects in the Brazilian clinical trial were medical staff, and the risk of infection in this group was high. The incidence of COVID-19 observed in the placebo group was 5 times higher than that of the general population in Brazil during the same period. The test also captured the mild symptoms of these subjects, such as sore throat, runny nose, and fatigue. Therefore, there are many mild cases of infected people who do not require any treatment.

Jin Dongyan, a professor at the School of Biomedicine of the University of Hong Kong and a virologist, told China News Weekly that medical staff are more careful. Once they become infected, they may be careful, or they may be tested more frequently. This is possible, making the vaccinated group better than other vaccines. More cases were captured in clinical trials, and the effective rate was diluted. However, “Phase III clinical trials were originally to be carried out in high-exposure and high-risk areas, so that it was possible to test whether the vaccine has protective effects and how high the protection efficiency is.” A scientist involved in the development of the COVID-19 vaccine pointed out.

Kexing vaccine has initially reported different values ​​in different clinical trials. The protective efficacy in Turkey is 91.25%, in Indonesia 65.3%, and in Brazil 50.38%. Kexing explained that although the protective efficacy of each test is different, the common result is that the vaccine has a clear protective effect, especially for moderate and severe symptoms. For example, in Brazil, all 7 hospitalized and severe cases occurred in the placebo group; in Turkey, all 6 hospitalized cases occurred in the placebo group, and the vaccine’s protective effect on hospitalization and severe illness was 100%.

Cui Xiang, who is engaged in vaccine research and development in the United States, explained that the meaning of Kexing vaccine can be understood so simply: the risk of contracting the new coronavirus is reduced by 50%, and the risk of going to the hospital due to COVID-19 is reduced. 80%, the risk of developing severe illness is reduced by 100%.

Many experts believe that the effectiveness of the same technical route should not be too different. It can be seen that the two mRNA vaccines from Pfizer and Moderna are both around 95% effective. As for why the two inactivated vaccines of China Biological and Kexing are quite different, we need to see the original data.

While the Chinese are paying close attention to the effectiveness of Chinese vaccines, the data of a foreign star vaccine also caused controversy. On January 4, “British Medical Journal” (BMJ) Deputy Editor-in-Chief Peter Dorsey stated on the magazine’s blog site that Pfizer’s vaccine is not 95% effective, but only 29%. The reason is that he believes that there may be a large number of false-negative nucleic acid tests among the 3,410 suspected COVID-19 patients in the clinical trial volunteers, so they should all be counted as infected, and the above results can be obtained after recalculation.

Zhu Fengcai, a clinical vaccinology expert and deputy director of the Jiangsu Provincial Center for Disease Control and Prevention, pointed out that this algorithm is unreasonable and extreme, because the symptoms of suspected patients may come from other diseases, and no positive nucleic acid test cannot be diagnosed with COVID-19. Among 3,410 suspected cases, The proportion of real infected people is not high. If according to Dorsey’s calculation method, the protective effect of all vaccines will now become less.

Cui Xiang told China News Weekly that it is unreasonable to question Pfizer’s “29%” protective effect. However, Pfizer’s clinical trial design is also worthy of scrutiny.

For example, in the double-blind design, the placebo group of the Oxford/AstraZeneca vaccine in the UK used recombinant adenovirus, but the delivery was not the COVID-19 gene, which was more rigorous; but the placebo group of the Pfizer vaccine used normal saline. There are few adverse reactions, and it is easier for researchers to distinguish which are vaccinated and which are not. The test is not a standard double-blind state. Zhu Fengcai also mentioned that the vaccine group may have more mildly symptomatic subjects than the control group. If these people do not report, the researchers will not know that they have been infected, and the final number of infected people will be lower. The vaccine has Efficiency will also be overestimated.

WHO: World will not achieve herd immunity for COVID-19 in 2021 

On December 8, 2020, in Coventry, UK, 90-year-old Margaret Keenan, the country’s first vaccinator, was welcomed by the staff when she returned to the ward after being vaccinated. Picture/People’s Vision

Although the data on the protection of vaccines has attracted the most attention, as a practitioner in the pharmaceutical industry said, there is no need to regard the level of effectiveness as a win or lose issue. As long as the vaccine proves useful, it has the potential to help us control the epidemic. . The most pressing issue at the moment is vaccination, vaccination, vaccination.


Challenges facing herd immunity in China

Recently, a cluster of epidemics broke out in many places in the country. Zhang Zuofeng, Distinguished Professor of Epidemiology at the School of Public Health at the University of California, Los Angeles, suggested that in view of the current arduous tasks of prevention and control, China may consider applying emergency COVID-19 vaccine to people who have tested negative at the outbreak site and the surrounding population while conducting large-scale testing. Vaccination, forming a “safety belt” to curb the spread of the virus.

How many people does a given population need to be vaccinated to establish herd immunity? According to an article published in the medical journal The Lancet by some scholars of Imperial College London in November 2020, assuming that the protection of the vaccine is permanent, when its effective rate is 100%, the vaccination rate required to establish herd immunity is at 60% to 72%; when the vaccine effective rate is 80%, the ratio is 75% to 90%; if the vaccine effective rate is less than 80%, everyone needs to be vaccinated.

WHO: World will not achieve herd immunity for COVID-19 in 2021

On January 3, the vaccinators participated in the inactivated COVID-19 virus vaccination at the temporary vaccination site set up at the Chaoyang Planning Art Museum in Chaoyang District, Beijing. After the vaccination, the personnel must stay in the observation area for 30 minutes before leaving. Photographer/Reporter Hou Yu

The National Health Commission’s Directorate of Disease Control and Prevention Wang Bin said at a State Council press conference held on the 13th that the key population for vaccination at this stage is the high-risk population aged 18 to 59. With the continuous improvement of vaccine clinical research data, the need for prevention and control, and the increase in vaccine supply, China will expand the target population of vaccination to more people, including the elderly 60 years and older.

Huang Yanzhong, senior researcher of global health at the US Council on Foreign Relations, analyzed to China News Weekly that Chinese vaccines currently cannot cover people under 18 and over 60, especially the elderly as high-risk groups, which is not conducive to the establishment of herd immunity. According to data released by the National Bureau of Statistics, at the end of 2019, the number of people aged 60 and over in China reached 254 million, accounting for 18.1% of the total population.

Another factor that affects vaccination rate is vaccination willingness. In October 2020, an article on the “Nature” website surveyed the potential acceptance of the COVID-19 vaccine in 19 countries and found that China had the highest acceptance, reaching 90%. However, Tao Lina, the former immunization planning physician of the Shanghai Centers for Disease Control and Prevention, said that due to the good Chinese epidemic prevention and control, many people believe that there is no need to vaccinate.

“It’s not about using or not, or whether to wait for a better vaccine to accelerate vaccination. What we are facing is the problem of supply.” Yu Li, a vaccine chief examiner who once worked at the FDA, told China News Weekly, as long as If you have a vaccine, you should be vaccinated to prevent local outbreaks like Hebei and Heilongjiang for a while.

By 2021, according to the production capacity plans of some Chinese vaccine research and development companies, China’s COVID-19 vaccine production capacity will exceed 2 billion doses. Kexing has completed the construction of the second production line and is expected to have an annual production capacity of 1 billion doses of COVID-19 vaccine after it is put into use in February this year. China Bioscience plans to provide 1 billion doses or more of vaccines to the whole of China in 2021. According to Cansino Bio, it plans to build a production capacity of 100 to 200 million doses of COVID-19 vaccine within this year; Fosun Pharma and BioNTech have reached an agreement that once the mRNA vaccine developed by the latter is approved for marketing in mainland China, it will be supplied to mainland China at least this year 100 million doses and so on.

“(Capacity) still has a certain gap, but not everyone needs to be vaccinated immediately. With a step-by-step and level-by-level vaccination strategy, I think these problems will be gradually resolved in the second half of this year.” President Zhang Yuntao said.

In terms of transportation and storage, inactivated vaccines in China are more convenient than mRNA vaccines used in Europe and the United States. Zhang Yuntao said that the storage conditions for inactivated vaccines are 2°C to 8°C, which is consistent with the storage and transportation conditions of all vaccines currently in China. For example, the vaccine of Pfizer in the United States needs to be stored at -70°C, and the vaccine of Moderna in the United States is -20°C. Such cold chain transportation conditions are currently not available in many Chinese cities, including Beijing.

“If vaccination in the United States can progress as planned, herd immunity can basically be achieved from June to August, and the situation in Europe is similar. If China cannot achieve this goal in a timely and effective manner, the epidemic may continue for a long time. “Zhang Zuofeng said.


Global vaccination speed competition

Due to various reasons such as economic strength and efficiency, countries are racing at different speeds in the current global vaccination competition.

According to the latest statistics from Bloomberg and other institutions on January 16, when most countries in the world have not yet received the first shot, Israel currently leads with a vaccination rate of 28.52%, closely followed by the UAE (18.34%). The United States, China, and the European Union rank in the top three in terms of inoculation doses, but in terms of inoculation rates, the United States (4.48%), the European Union (1.29%), and China (0.71%) rank 5, 17, and 37 in that order.

 WHO: World will not achieve herd immunity for COVID-19 in 2021

On January 16, India began to carry out COVID-19 vaccination nationwide. Outside a hospital in Mumbai, front-line medical staff lined up for vaccination. Picture/People’s Vision

Israel uses the American Pfizer vaccine and Moderna vaccine. Calculated according to its 95% effective rate, the vaccination rate required to achieve herd immunity ranges from 65% to 75%. In this way, it may be the first country to realize it. There are many reasons for Israel’s rapid advancement, such as sufficient supply. This country with only 8.8 million people ordered 8 million doses of COVID-19 vaccine from Pfizer in November last year. On the other hand, Israel has launched a large-scale public health mobilization, so the public’s willingness to vaccinate is high.

In the United States, where the epidemic is the most severe, since the two vaccines were put into emergency use in mid-December last year, the most critical issue is how to roll out vaccination faster. The United States hopes to complete 100 million vaccine injections in the first 100 days of 2021, that is, 1 million a day, but it has not yet reached it. 

WHO: World will not achieve herd immunity for COVID-19 in 2021

Data from the Centers for Disease Control and Prevention of the United States shows that as of January 8, the agency has distributed more than 22 million doses of vaccine to states and other jurisdictions. At this point, only 6.7 million people have completed the first dose. The original goal of the United States was to vaccinate 20 million doses of vaccine by the end of 2020. It can be seen that the promotion efficiency is much slower than expected. The reasons include catching up with holidays, hesitation in the initial stage of vaccination, and the state’s uncertainty about who can be vaccinated. Anthony Fauci, the chief infectious disease expert in the United States, believes that the United States could have done better in terms of the speed of vaccination. “(The goal) is clear and there are no excuses. I think we have to wait until the first few weeks of January to determine what has happened. Only by question can we judge whether the speed can catch up with the original goal.”

To speed up the advancement, on January 12, the U.S. Department of Health and Human Services has notified the states to immediately expand the pool of vaccinated populations to include all elderly 65 years and older and vulnerable groups with underlying diseases. The vaccine will be based on the number of elderly populations in each state. And vaccination rate rather than the state population.

Under the suggestion of the federal government, some states have expanded the scope of vaccination and thousands of people are applying for vaccination. But these states found that they were in a new predicament: the vaccine did not arrive as scheduled, and the government did not actually have excess inventory. Because of the confidence in supply, it is believed that the three-week interval between the two injections can replenish the production capacity. The US “operation warp”, which is responsible for the distribution of vaccines, has stopped storing the second dose of Pfizer/BioNTech vaccine at the end of 2020. This weekend, the final inventory of Moderna vaccine is already on the way.

Because of the widespread spread of the mutant virus, British Chief Medical Officer Chris Whitty said that as many high-risk groups as possible should be protected by the vaccine in the shortest possible time. The latest data on January 16 shows that the UK ranks fourth in the world with a vaccination rate of 6.67%.

Originally, the interval between the two doses of the Oxford/AstraZeneca and Pfizer vaccines should be four and three weeks. However, on December 30, 2020, the British government notified that the time for the second vaccine was extended to 12 weeks. after. In the current situation of vaccine supply shortage, in order to expand coverage, in addition to the United Kingdom, Denmark, Germany and other countries are also considering adjusting the vaccination procedures and delaying the second injection.

According to Lu Mengji, a German Chinese virologist and professor at the Institute of Virology at the University of Essen’s School of Medicine, generally speaking, the immune response in the body is activated after the first shot, and it will gradually return to its original state after at least 3 to 4 weeks. One immunization cycle, and then a second injection to strengthen long-term immunity. Therefore, Pfizer and Moderna vaccines chose an interval of 21 days and 28 days, respectively. “21 days and 28 days is the lower limit, not less than this time, but it can be pushed back. In theory, the more delayed the vaccination, the better the immune boosting effect produced by the second shot.” He said.

Professor Chen Zhengming of the University of Oxford said that academic circles have also debated whether vaccination can be delayed, but for the UK, it is really helpless. Regardless of the number of new infections, hospitalizations or deaths, the current epidemic in the UK has approached or even exceeded the first wave in early 2020. Moreover, the mutant strain spreads very quickly. The longer the epidemic lasts, the more likely there will be more new mutations. In such an emergency situation, it is necessary to expand the coverage of vaccination as soon as possible to catch up with the spread of the mutant virus.

However, Sumia Swaminatan, the chief scientist of the World Health Organization, recently pointed out that even if vaccines begin to protect the most vulnerable groups, the world will not achieve any degree of herd immunity in 2021. It may be realized in a few regions or countries, but it is not global. She urged people to continue to strictly maintain social distancing this year


(source:internet, reference only)

Disclaimer of