New crown vaccine can prevent more than 95% of severe illness and death?

*Read only for medical professionals.
Although the battle against the new coronavirus has dawned, we must not let our guard down
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On March 22, the Li Ka Shing Faculty of Medicine of the University of Hong Kong published research data on the protective power of the new crown vaccine against the Omicron variant in the fifth wave of the epidemic on the preprint platform medRxiv.
3 doses of inactivated vaccine and mRNA vaccine prevent different ages.
The effectiveness of the severe and death crowd is over 95%, the effectiveness of 3 doses of inactivated vaccine in preventing mild to moderate COVID-19 is over 40%, and the effectiveness of 3 doses of mRNA vaccine is over 70% (Table 1) [1]
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Table 1.
Effectiveness of different vaccine types and doses against mild/moderate illness, severe/fatal illness and death of COVID-19 [1] This result is undoubtedly a hopeful good news for us who have been suffering from the epidemic recently, but A closer look at the research suggests that perhaps we can't be too optimistic just yet
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why would you said this? In the process of design and development of each study, there will be certain limitations due to the time, environment and characteristics of the population, and this study is no exception
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First, the researchers mentioned in the text that "in this study, vaccine efficacy, especially for serious outcomes, may have been overestimated"
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This is closely related to the characteristics of Hong Kong vaccinators
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The so-called "healthy vaccinee bias" occurs in this case because the vaccination rate is lower in the elderly and people with underlying diseases in Hong Kong
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The vaccinated population is healthier than the unvaccinated population, so the vaccinated gets double protection
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On the one hand, the protection from vaccines, on the other hand, a healthier body will also protect them from severe illness and death
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This bias may therefore lead to overestimation of effectiveness
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Another limitation that deserves our attention is evaluation time
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The data included in the study were as of March 8, and it can be seen from Table 2 that the median time from the third dose of vaccine to positive diagnosis was only 35-66 days
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Therefore, this study can only assess the short-term efficacy of the vaccine
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Table 2.
Median days between last vaccination and positive SARS-CoV-2 test [1] Vaccines are at peak protection shortly after vaccination, while Covid-19 vaccine protection decreases over time gradually decline
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Also in the Li Ka Shing School of Medicine of the University of Hong Kong, another study published on EBioMedicine on March 3 showed that 3 months after BNT162b2 and CoronaVac two new crown vaccines, neutralizing antibody titers and T cell responses were both reduced to varying degrees
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Levels of neutralizing antibodies against the variant (VOC) were reduced to near the limit of detection, and memory T cell responses were attenuated, mainly in CoronaVac vaccinators (Figure 1) [2]
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Figure 1.
Changes in humoral and cellular immune responses in BNT162b2 and CoronaVac vaccinated individuals from the initial vaccination phase to the memory phase [2].
Real-world studies have also demonstrated a gradual decline in protection over time
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A study published by the Malaysian Ministry of Health compared "early vaccination" (full vaccination from April to June 2021) and "late vaccination" (2021 fully vaccinated July-August 2010) differences in vaccine effectiveness between the two groups
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In preventing ICU admission, the effectiveness of 2 doses of BNT162b2 decreased from 86.
0% at 1-2 months after vaccination to 77.
5% after 3-5 months, and the effectiveness of 2 doses of CoronaVac decreased from 56.
0% to 28.
7%
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The two vaccines showed smaller declines in preventing deaths, with 2 doses of BNT162b2 decreasing from 91.
5% 1-2 months after vaccination to 91.
2% 3-5 months after vaccination, and the effectiveness of 2 doses of CoronaVac decreasing from 79.
2% to 76.
2% % (Table 3) [3]
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Table 3.
Effectiveness of vaccines to prevent ICU admission and death as assessed by vaccine type and duration after vaccination The cases were all in the elderly population, and during the fifth wave of the epidemic, the vaccination rate of the elderly was very low
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Most of the third-dose vaccine recipients were recently vaccinated
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The attenuation effect has not been studied in this analysis, and the team will start it as soon as possible.
Relevant studies but more data need to be collected
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”
In addition, the researchers also mentioned that based on the current data, it is not possible to compare the protective power of the two schemes of heterologous sequential boosting and homologous boosting
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The Hong Kong Department of Health has previously recommended a third dose of BNT162b2 as a booster in adults who received two doses of CoronaVac, but currently only 26% of all adults who received two doses of CoronaVac and received the third dose received the third dose BNT162b2
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Therefore, more data are needed for evaluation and comparison
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Although it will take some time to obtain more comprehensive data, there is no doubt about the importance of the third dose, at least in the short term, the two vaccines can provide effective protection against severe disease and death
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Most of the deaths in Hong Kong's fifth wave of the epidemic were unvaccinated or under-vaccinated elderly people (Figure 2) [4], which reminds us that booster vaccination of the elderly is the top priority of the next immunization strategy
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Figure 2.
The cumulative number of deaths from the fifth wave of the epidemic in Hong Kong[4] The vaccination status of the elderly in my country was announced at the press conference of the State Council Information Office on March 18
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As of March 17, 88.
8% of the elderly in China aged 60 to 69 received a single dose, 86.
6% of the elderly who completed the whole course of vaccination, and 56.
4% of the elderly who completed the booster immunization; 86.
1% of those aged 70 to 79 , 81.
7% and 48.
4%; people over the age of 80 were 58.
8%, 50.
7% and 19.
7% [5]
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It can be seen from the figures that the vaccination rate of the elderly, especially the elderly, needs to be improved urgently
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Most of the elderly have underlying diseases.
How to promote vaccination more scientifically and effectively, while dispelling various concerns of the elderly and their children is an urgent problem to be solved.
The vaccination rate of the elderly will have a significant impact on future epidemic prevention strategies
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Summary: Although the data on the protection of inactivated and mRNA new crown vaccines against Omicron variants in Hong Kong on March 22 is encouraging, the limitations such as “healthy vaccinator bias” and “only short-term efficacy was assessed” reminded us We can't be too optimistic, and more long-term and comprehensive data are needed for a comprehensive assessment
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Three doses of the vaccine can effectively prevent severe illness and death within a short period of time after vaccination.
Therefore, accelerating the booster vaccination, especially the completion of the basic immunization and booster immunization for the elderly, is an urgent priority
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We have seen the light of day and believe that spring will come soon
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References: [1] McMenamin ME, Nealon J, Lin Y, et al.
medRxiv 2022.
03.
22.
22272769.
doi: https://doi.
org/10.
1101/2022.
03.
22.
22272769 [2] Peng Q, Zhou R, Wang Y, et al.
Waning immune responses against SARS-CoV-2 variants of concern among vaccinees in Hong Kong.
EBioMedicine.
2022 Mar 3;77:103904.
doi:10.
1016/j.
ebiom.
2022.
103904.
Epub ahead of print.
[3]Suah JL, Husin M, Keng PS, et al.
Waning COVID-19 Vaccine Effectiveness for BNT162b2 and CoronaVac in Malaysia: An Observational Study.
International Journal of Infectious Diseases.
2022 Mar 22.
https://doi.
org/10.
1016/j.
ijid.
2022.
03.
028.
[4] 5th wave of COVID-19 data (as of March 26) https:// State Council news on March 18 Office Press Conference http:// This information is for medical and scientific reference only, and does not constitute any drug Or the recommendation and promotion of treatment programs
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The information contained in this article should not be used as a substitute for medical advice from a healthcare professional
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