Zhang Wenhong: To raise the full vaccination rate of the new crown vaccine to 90% for people over 60 years old as soon as possible

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How can we protect this vulnerable group of the elderly? Vaccination remains one of the most critical and effective practices.

“Currently, the nation faces a huge challenge of hundreds of millions of new crown infections. In the long run, whether the mutation of the virus will cause some immune escape is causing widespread concern.” Zhang Wenhong, director of the Department of Infectious Diseases at Huashan Hospital of Fudan University, said at a training series on “Standardized Treatment of Critically Ill Patients with New Coronary Infections and Underlying Diseases” on the evening of the 2nd.

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A medical study in Shanghai recently said that 30 known strains of Omicron were identified by genetic sequencing in randomly collected samples of patients with NICU from Nov. 23 to Dec. 22, 2022, while the XBB and XQ strains, which are prevalent in the United States, are considered by scientists to have strong “immune escape” capabilities.

Will virus mutations cause escape from existing vaccines? According to Zhang Wenhong, since 2022, the team has found that the mutation rate of the new coronavirus is very fast, and there are many subgroups of the virus in patients at the same time (more than 20% of the subgroups are inconsistent with the major subgroups), which means that after vaccination and herd immunization, these mutation points, or subspecies with the potential to escape, are constantly screened out.

“Currently, the country is dominated by strains of BA.5 or BF.7. If one has already been infected with BA.5 or BF.7, we will be quiet for a while after this wave, and then a small number of new subtypes such as XBB and BQ.1 may mutate subsequently.” So far, Zhang Wenhong said, the new crown is a seasonal epidemic caused by small mutations, judging from the characteristics of antigenic drift, mutations in surface genes and the existence of different degrees of preexisting immunity in the population.

If vaccination and herd immunization will have the possibility of escape as mentioned above, is vaccination still useful?

Zhang Wenhong said that data from several countries and regions around the world have made it clear that whatever the subtype of the Omicron strain, it always exerts some cross-immunity, “so the full vaccination with the new crown vaccine is a very definitive protective factor.”

Zhang Wenhong said, taking the situation in Shanghai in the first half of 2022 as an example, “it was a BA.2 strain at that time, and after analysis of heavy patients in sentinel hospitals, it was found that the adjusted risk (dominance ratio) of patients who had received the New Crown vaccine could be reduced to 0.214, which means that the protection rate for severe disease could reach 78.6%. Thus, cross-immunization, although it does not block the patient from infection, has a very definite protective effect against severe disease.”

“Again, in Singapore and the United Kingdom, and in the United States, for example, they all have a larger proportion of full and booster vaccinations, especially when they encountered the first wave of deaths after liberalization, and then they rapidly increased the rate of vaccination; with this practice, the number of infections in Omicron has increased, but the rate of death from disease has continued to decline. Including Hong Kong, China, and Taiwan, China, where the number of infections increased substantially after the first wave of liberalization, once vaccination caught up, their subsequent morbidity and mortality rates were also lower.”

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So, what vaccination strategy should be chosen for the different technical routes of the new crown vaccine that are currently available?

According to Zhang Wenhong, the team’s Meta-analysis shows that overall, the protection rate is 73.11% for inactivated vaccines, 79.56% for adenovirus vector vaccines, 89.33% for subunit vaccines, and 94.29% for mRNA vaccines.

In order to keep up with the overall vaccination, Wenhong Zhang suggested that a sequential strategy of “two doses of inactivated vaccine + recombinant protein vaccine booster” could be used, which improves the overall potency of the new coronavirus variant, and he also indicated that BA.2 breakthrough infection significantly increased the neutralizing antibody titer compared to the homologous and heterologous vaccine booster groups. antibody titers, and both BA.2 and its derivative variants and BA.4/5 maintained high neutralizing activity.

For this wave of the outbreak, how did the two groups of vaccinated and unvaccinated people fare differently after infection?

According to Wenhong Zhang, patients who are infected after vaccination can obtain a good “mixed immunity (protection by both pre-existing vaccine antibodies and natural antibodies),” which can build an immune barrier against Omicron. So far, we have not found any cases of re-infection with the BA.5 strain after mixed immunization.”

“Therefore, the next step is to complete the drug stockpile as soon as possible based on the base of people with high-risk factors mapped by provinces and municipalities, when antiviral drugs can be covered for 100% of patients with high-risk factors, it will effectively reduce their rate of severe disease. At the same time, the full vaccination rate for people over 60 years old will be raised to 90% as soon as possible.”