"Further vaccinations with more effective vaccines will eliminate the threat of COVID-19 at the least cost in the future."
Written by | Lingjun
Source | "Medical Community" public account
On April 18, local time, Brazilian Health Minister Marcelo Queiroga announced that the use of the Coxing inactivated vaccine will be limited to children and adolescents between 5 and 18 years old, and withdraw the vaccine from the national adult immunization program.
According to Brazil's São Paulo newspaper, inactivated vaccines played an important role in the country's COVID-19 vaccination programme early on, accounting for 85% of the total number of vaccinations by March 2021. But then it was gradually replaced by vaccines from other technical routes, and the proportion of vaccinations fell to less than 10% at the end of last year.
The same thing happened in Chile. Chile is also one of the countries that use the Coxing inactivated vaccine on a large scale, with more than 25.18 million doses of inactivated vaccines as of January 21, 2022 local time. But a recent study showed that of the more than 4 million people in Chile who received two doses of inactivated vaccines, only 4.5% of the people who followed up chose the inactivated vaccine for the third dose.
inactivated vaccine protection decreased,
Brazil replaces the "vaccination regimen"
The Coxing inactivated vaccine is a "pioneer" in Brazil's fight against the epidemic.
On January 17, 2021, Brazil's National Medicines Agency approved the emergency use of the Coxing inactivated vaccine, followed by a large-scale real-world study in the city of Serrana, brazil. The results released in May of the same year showed that after full vaccination with inactivated vaccines, the number of new LOCAL COVID-19 cases fell by 80%, the number of hospitalizations fell by 86%, and the number of new deaths fell by 95%.
But over time, there is evidence that the protective power of two-shot inactivated vaccines has been greatly attenuated.
On March 30, academics at research institutions in Brazil and the United States released a large real-world study on the preprint platform medRxiv, which included more than 2.6 million people in Brazil, and the results showed that the original two-shot inactivated vaccine vaccinators during the engulfment of the Aumechon variant:
The third dose was homologously strengthened with inactivated vaccine, and the effectiveness of anti-COVID-19 infection was 15% after 8-59 days, and the effectiveness of anti-severe disease was 71.3%, while the corresponding data were 56.8% and 85.5% after strengthening with mRNA vaccine.
At the same time, the researchers also explored the degree of attenuation of the vaccine's potency. The relative effectiveness of the third dose of inactivated vaccine for 8-59 days was 42% in the prevention of severe illness or death compared with two doses of inactivated vaccine, but further attenuation was 14.8% after three months.
In contrast, the heterologous enhanced protective effect of mRNA vaccine was relatively stable, and it was still 66.9% after three months.
From the perspective of humoral immunity, in another study, Brazilian scholars tested antibody titers on 1205 people, and the results were published in the top issue "The Lancet" on February 5, 2022.
A 2-dose primary dose of inactivated vaccine was also completed, and the neutralizing antibody titer of the mRNA vaccine or adenovirus vaccine booster group was increased by 6.4-12.6 times compared with the continuation of the third inactivated vaccine. In the elderly group, this proportion rises further to 8-22 times.
Although these trials have many limitations at the design level, and the absolute value of the results cannot be directly used to compare with other studies, the relative ratios within the trials still provide guidance for vaccination regimens.
According to the São Paulo newspaper, because inactivated vaccines are often less effective than other types of mainstream vaccines in the face of Delta and Omicron variants, the federal government and many states have subsequently excluded inactivated vaccines from the new vaccination program.
Singapore: Two doses of inactivated vaccine are not complete
Similar results have appeared in large real-world studies in Singapore and Chile.
On 12 April, Singapore scholars published a paper in Clin Infect Dis that, after analyzing the infection of 2.7 million people after vaccination, the results showed:
If the risk of COVID-19 infection after receiving two doses of Pfizer inactivated vaccine is set as 1, the risk of Modena mRNA-1273 vaccine, Kexing inactivated vaccine and Sinopharm inactivated vaccine is 0.84, 2.37 and 1.62, respectively;
If the risk of severe COVID-19 infection after receiving two doses of Pfizer inactivated vaccine is also set as 1, the risk of the other three groups is 0.42, 4.59 and 1.58, respectively.
This means that the two doses of Pfizer mRNA vaccine are assumed to have a 90 percent protection against severe COVID-19, while mRNA-1273, CoronaVac, and BBIBP-CorV are 96 percent, 54 percent, and 84 percent, respectively, the researchers said.
Comparison of the efficacy of the four vaccines
It is reported that from August 30, 2021, sinopharm inactivated vaccine is allowed to be used in private medical institutions in Singapore, and the Kexing inactivated vaccine is still on the vaccine list of Singapore's national immunization plan.
But as of 30 November 2021, only about 70,000 people in Singapore have been vaccinated. Because of the relatively low effectiveness, on December 2, 2021, the Ministry of Health of Singapore issued the "Reminder for Completing the Primary Series of COVID-19 Vaccines and Sinopharm Vaccines", which strongly recommends:
People who have received two doses of inactivated vaccine should receive a third dose of mRNA vaccine for heterologous vaccination, unless mRNA vaccine is not suitable for health reasons, such as allergies.
Shortly thereafter, the Singapore government issued a new policy stating that from 2022 onwards, people who have received only two doses of inactivated vaccine will no longer be considered "completed with basic vaccination".
Researchers in Chile have also called for a worrying decline in the protective power of inactivated vaccines because of their relatively low initial protective effect. For people who have completed two doses of inactivated vaccination, xogenous boosting with mRNA or other technical route vaccines should be prioritized.
The study was published the day before yesterday (April 23) in The Lancet Global Health. Yesterday, the "medical community" published in "What is better to strengthen the selection of injections after two inactivated vaccines?" Chile publishes real-world data on nearly 9 million people" reports:
The results of real-world research of nearly 9 million people suggest that on the basis of two doses of inactivated vaccine, the third dose continues to be homologously strengthened with inactivated vaccine, and the relative effectiveness of infection prevention, hospitalization prevention, severe illness prevention and death prevention is 63.8%, 59.3%, 71.2% and 62.7%, respectively.
The relative efficacy of the mRNA vaccine or adenovirus vaccine was 93.5%, 86.6%, 84.1%, 90.7%, 88.4%, 93%, 95.9%, and 94.7%.
Experts are calling for the introduction of a more effective vaccine
On March 25, the joint prevention and control mechanism of the State Council held a press conference to disclose that as of March 24, 2022, the mainland had completed the full covid-19 vaccination rate of 88.01%.
Booster immunization was completed for 671.27 million people (about 47.5%), of which only 12.191 million were under a cross-vitamin programme.
According to this data, the proportion of people in the mainland who have completed three doses of vaccine booster immunization is not high. A large number of studies around the world suggest that relying solely on two doses of inactivated vaccines may not provide enough protection to deal with future virus threats without "natural infection immunity".
Zhang Hongtao, associate professor of pathology and laboratory medicine research at the University of Pennsylvania, previously said to the "medical community" that in terms of the accessibility of the vaccine, inactivated vaccines have laid a "basic herd immunity" for the population, on this basis, if there is a choice, it should still be vaccinated with a better vaccine as a reinforcing needle, and the introduction or acceleration of the development of mRNA vaccines is "urgent" whether it is to alleviate the current epidemic situation or lay out the future.
"The key to building a vaccine defense line is that vaccines can stimulate a diverse immune response. Both mRNA vaccines and viral vector vaccines have very good effects, not only can stimulate antibodies, but also induce cellular immunity, better prevent severe illness and death. Lu Mengji, a German-Chinese virologist and professor at the Institute of Virology at the University of Essen School of Medicine, said, "In contrast, the effect of inactivated vaccines is poorer." ”
Judging from the vaccination programs in Brazil and Chile, after the previous large number of inactivated vaccines, the local government also recommended the use of other technical routes for enhanced vaccination. According to data from airfinity, a health data analytics company, Indonesia and Pakistan are also the largest recipients of inactivated vaccines, but the number of boosters used for inactivated vaccines is much smaller.
These real-world vaccination protocol adjustments, as well as trial-related data, should also provide some degree of advice and guidance for subsequent vaccination strategies on the mainland, that is, for a large number of people who have not yet received a third booster, sequential vaccination with mRNA vaccine or adenovirus vaccine should be a priority.
"Among them, the mRNA vaccine is the best solution, and the disadvantage of the viral vector vaccine is that the antibody titer produced is relatively low." Lu Mengji said.
Lu Mengji believes that the current "dynamic zero clearance" policy provides China with a long "protection period", and it is necessary to seize this opportunity to obtain sufficient basic immunization of the population through further vaccination of more effective vaccines, so that the population can get enough basic immunization in order to eliminate the threat of the new crown virus at the least cost in the future.
bibliography:
[1] Folha de S.Paulo:Previously essential, coronavac is now in danger of being left out in Brazil,https://agenciaaids.com.br/noticia/folha-de-s-paulo-antes-essencial-agora-coronavac-corre-risco-de-ser-left-de-lado-no-brasil/
[2] Brazil’s Experiment to Vaccinate Town With Chinese CoronaVac Reduced Covid-19 Deaths by 95%,dhttps://www.wsj.com/articles/brazils-experiment-to-vaccinate-town-with-chinese-coronavac-reduced-covid-19-deaths-by-95-11622479864
[3] Effectiveness of an Inactivated Covid-19 Vaccine with Homologous and Heterologous Boosters against the Omicron(B.1.1.529)Variant，https://www.medrxiv.org/content/10.1101/2022.03.30.22273193v1.full-text
[4] Scientists urge China to replace its faltering Covid vaccines，https://www.ft.com/content/729f1dc0-32d1-42c9-bb62-63a41f1e8de2
[5] Heterologous versus homologous COVID-19 booster vaccination in previous recipients of two doses of CoronaVac COVID-19 vaccine in Brazil(RHH-001):a phase 4,non-inferiority,single blind,randomised study，https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(22)00094-0/fulltext#%20
[6] Those with 2 doses of Sinovac can walk in to selected vaccination centres for third jab:MOH，https://www.todayonline.com/singapore/those-2-doses-sinovac-can-walk-selected-vaccination-centres-third-jab-moh-1778526
Source: Medical community
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Proofreader: Zang Hengjia
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