The "fourth shot" in many places: different doses at each vaccination site, "Yang Kang" people to play?

Read Time:10 Minute, 17 Second

With the rapid spread of variant strains of the New Coronavirus, high-risk populations such as the elderly continue to be at risk of infection, and further strengthening of preventive measures is urgently needed. Currently, the coverage of the first booster dose of the neo-coronavirus vaccine in China’s elderly population has yet to be expanded, and the second booster dose of the vaccination program focusing on the immune-vulnerable population has been officially launched in many places across the country.

The State Council’s Joint Prevention and Control Mechanism Integrated Group issued the “Implementation Plan for the Second Dose of New Coronavirus Vaccine Booster Vaccination” (hereinafter referred to as “Implementation Plan”) on the 13th, proposing that at this stage, on the basis of the first dose of booster vaccination, the second dose of booster vaccination can be carried out in people at high risk of infection, elderly people over 60 years old, people with more serious underlying diseases and people with low immunity. The second dose of booster immunization can be carried out among people with high risk of infection, elderly people over 60 years old, people with more serious underlying diseases and people with low immunity.

The implementation plan was released just a week after the launch, and as of the 20th, Beijing, Shanghai, Guangzhou, Shenzhen, Changsha, Shijiazhuang, Zhengzhou, Haikou, Chongqing and many provinces and cities such as Zhejiang, Jiangsu and Anhui have officially started the vaccination, with different doses offered by different regions and vaccination units,” Firstrade found.

“Vaccination has been carried out by the hospital’s preventive health department, and since the 16th, our community hospital has been able to administer the second dose of booster shots. However, there are several problems in the work: firstly, the only vaccine available in our hospital is the recombinant New Crown vaccine from Zhifilongkoma; secondly, among the people who have recently come to consult for the fourth dose, part of them are young and middle-aged people or people who have just ‘yangkang’, and a considerable percentage of senior citizens in the community have not yet started the first dose of the booster. ” A community hospital medical staff in Chongqing told First Financial.

In the context of the recent rapid increase in new crown infections in many places, will vaccination not increase the risk of exposure to immunologically vulnerable people? If infected at the time of vaccination, can the fourth shot work in time? Is it necessary to give the fourth vaccination in a short period of time after “Yang Kang”?

How effective is the “fourth dose”?

The new “fourth vaccination” for special groups was opened and spread rapidly in many places in China.

In the evening of the 19th, Hefei Shushan District’s official WeChat public number “Shushan Release” issued a message saying that in order to further improve the response to the new crown pneumonia epidemic, to protect people’s lives and health, and to facilitate the general public to carry out the second dose of booster immunization, the Anhui Provincial Health and Health Commission, together with the Anhui Provincial Data Resources Management Bureau, relying on the The Yangtze River Delta Government Map health and health theme map, launched the new crown vaccination point inquiry service. The general public can look up information about New Crown vaccination sites on the Yangtze River Delta Government Map, find the most convenient vaccination sites around them and go for the second dose of booster vaccination.

On the 20th, First Financial learned from the community health service centers in many districts of Hefei that the second dose of booster vaccination in the city has been officially launched. The doses offered at different vaccination sites vary, with some sites offering inhalation New Crown vaccine for eligible booster vaccine recipients and others saying that only two types of inactivated vaccines, Kexing and Kangtai Biological, are available.

In Fuyang, another city in Anhui, a local district issued a “notice on the full implementation of the booster vaccination for the new coronavirus vaccine” on the 16th, refining the second dose of the booster vaccination program into three categories: first, those who have completed three doses of inactivated vaccine can choose to receive the second dose of the booster new coronavirus vaccine at will; second, those who have received two doses of the adenovirus vector vaccine can choose to receive the second dose of the new coronavirus vaccine. vaccine that has already received two doses (without distinguishing between inotropic and inhalation vaccine, which cannot be used for first-time vaccine recipients), only the adenovirus vector vaccine booster can be used; thirdly, those who have received the first dose of inactivated two-dose + sequential booster vaccination will use the vaccine used for the first dose of the booster [distinguishing between vaccine types (e.g. recombinant vaccine, adenovirus vector vaccine), without distinguishing between manufacturers].

“Full vaccination with 3 doses of Anhui Zhifilongkoma protein recombinant (CHO cells) vaccine and people under 18 years of age temporarily do not need to have the second booster dose.” The notice prompted.

Not only Anhui, the first financial 20 as a vaccinator called a number of vaccination units in Shenzhen, Shijiazhuang, Chongqing, Shanghai and other places, the relevant staff have said that the current dose for the second dose of booster immunization reserves sufficient, but the dose is relatively limited.

“Our vaccination service for the fourth dose is not limited to immunologically vulnerable people. As long as you haven’t had a new crown recently, you can come to us for the fourth shot after making an appointment. However, if your first three shots are inactivated vaccines, we can’t provide sequential boosters for now.” The staff of a vaccination unit in Shenzhen told reporters.

At this stage, the four types of new coronavirus vaccines that have been approved for inclusion in our country for emergency use or conditional listing are inactivated vaccine, recombinant protein vaccine, adenovirus vector vaccine and influenza virus vector vaccine.

According to the implementation plan, all vaccines approved for conditional listing or emergency use can be used for the second dose of booster immunization, but “priority should be given to sequential booster immunization” or “the use of vaccines containing Omicron strains or with good cross-immunity to Omicron strains “.

Sequential booster immunization refers to heterologous booster immunization using vaccines of different technical lines. Several domestic and foreign studies have shown that heterologous booster immunization with vaccines of different technical routes can obtain higher levels of neutralizing antibodies.

Considering that the vast majority of vaccinees in China use three doses of inactivated vaccine during the pre-vaccination process, in the second dose of booster immunization, either recombinant protein vaccine, adenovirus vector vaccine or influenza virus vector vaccine can be selected, which is the eight vaccination combinations recommended by the implementation plan enumeration. In addition, the implementation plan also recommends another vaccination method: “2 doses of Convivox intramuscular adenovirus vector vaccine + 1 dose of Convivox recombinant neocoronavirus vaccine for inhalation”.

File photo

“This week, significantly more people have come for consultation than have actually been vaccinated (with the fourth dose).” The above-mentioned medical staff of a community hospital in Chongqing told reporters.

She said Chongqing has experienced a wave of peak infections since late November, and many locals have just “yanged through recovery. These people, some because of the infection experience “unpleasant to look back”, some people want to “superimpose the effect of immunity”, to consult the “fourth injection” many people, but these people do not meet the second However, these people do not meet the time interval requirement for the second dose of booster immunization.

“The number of seniors who have actually completed the fourth vaccination is still relatively limited.” The medical staff said, firstly, the group of elderly people who have completed the booster immunization in the community is still very limited, and even if they do, few of them have reached the six-month interval; secondly, during the peak period of infection, the risk of cross-infection during vaccination is greater, and some families of senior citizens with combined underlying diseases do not choose to bring their elderly in and out of the hospital at this time.

Do “Yang Kang” and non-immune vulnerable people need to play

Up to now, China has adjusted the interval between the booster vaccination and the basic vaccination for the elderly from 6 months to 3 months, but the interval between the second booster vaccination and the first booster vaccination for any group of people needs to be more than 6 months.

The interval between the second dose of booster immunization and the first dose of booster immunization for any population should be more than 6 months.

The director of the Beijing CDC’s Immunization Institute, Suo Luodan, mentioned on the 19th that according to the current national technical guidelines for the use of the NCC vaccine, reinfection within 6 months after a positive NCC virus infection is rare. People with previous New Coronavirus infection (patients or those with asymptomatic infection) can receive one dose after 6 months on the basis of adequate information.

“The cycle of vaccination is generally measured by two factors: the degree of decline in the protective effect of the vaccine, i.e., the duration of antibody maintenance after the most recent vaccination, and safety.” A New Coronavirus researcher told Firstrade.

He said that for non-immune vulnerable people who have received three doses of the vaccine, especially after an infection, the “memory” in immune B cells persists even six months after the most recent antibody production, which means that the existing antibodies are still effective against severe illness and death. On the contrary, it is unnecessary and unsafe to reinforce the immune system in the short term after the production of natural antibodies, which is equivalent to another shock to the body’s immune system.

In the expert’s opinion, the reason why the elderly and other immune-vulnerable people need to be vaccinated with the “fourth shot” is twofold: firstly, the decline in the level of neutralizing antibodies in the elderly is more significant over time; secondly, these people are at risk of serious illness after infection with the new coronavirus, and therefore need to have a constant body Therefore, the “relatively strongest state of immune protection” needs to be present at all times.

As for the reason behind the “vaccination hesitation” of some elderly people mentioned by the aforementioned grassroots vaccinators, that is, vaccination may increase the risk of exposure at a time when the number of positive infections is steeply increasing, the expert believes that this should indeed be taken seriously. However, theoretically, the vaccine can still provide some immune protection if one is infected during vaccination or on the way back home.

So, is the New Coronavirus vaccine only valid for 6 months? What is the next step of the neo-coronavirus vaccination?

Wang Huaqing, chief expert in immunization planning at the Chinese CDC, said at a press conference held by the State Council’s Joint Prevention and Control Mechanism on the 20th that the new coronavirus vaccine produces protective effects after vaccination, one is that it produces antibodies, and the other is that it produces cellular immunity and also immune memory. After vaccination, the level of antibodies decreases over time, and in addition, as the virus mutates, the immune escape is also increasing, making the role of antibodies in further weakening. However, cellular immunity, in particular, plays a more lasting role in preventing severe illness and death.

Studies have shown that by administering booster shots, the body’s immune memory cells are evoked on the one hand, and on the other, antibody levels are boosted, further consolidating the preventive effect against serious illness and death. “Therefore, we still emphasize that those who have not completed the booster immunization, as long as they are eligible for the vaccination, should complete the booster as soon as possible in accordance with the provisions of the immunization program to provide better protection. Of course, we should subsequently evaluate the effect of booster immunization systematically and continuously improve the immunization strategy.”

In the future, whether it is vaccine development or improvement of existing vaccines, Wang Huaqing said it is important to work on two aspects: the first is to consolidate the achievement of lasting and widespread protective immunity; the second is to make further efforts in terms of blocking infection and preventing transmission.