Strengthening vaccinations for the elderly "cannot be delayed"
Written by | Ling Jun
Source | "Medical Community" public account
On 12 April, Singapore scholars published a real-world retrospective study on the efficacy of different types of COVID-19 vaccines in Clin Infect Dis.
The study, which included more than 2.7 million people in Singapore, compared the effectiveness of two mRNA vaccines: BNT162b2, mRNA-1273 and two inactivated vaccines: CoronaVac, BBIBP-CorV.
Real-world data show that the mRNA-1273 vaccine is the most effective in preventing breakthrough infections and severe COVID-19. The least effective was CoronaVac, where vaccinators had a 4.69-fold higher risk of severe illness after COVID-19 than those who received the BNT162b2 vaccine.
"Three doses of inactivated vaccine are considered basic vaccination"
As of 14 April 2022, Singapore had a cumulative covid-19 infection of 1152117, with a total of 1,309 deaths and an infection case fatality rate of about 0.11%.
After the arrival of the Omikejong mutation, although Singapore experienced a wave of peak outbreaks, the infection mortality rate fell further. According to the Singapore Ministry of Health, 99.7% of the 162257 COVID-19 infections in Singapore in the past 28 days were mild or asymptomatic, and the infection mortality rate was only 0.04%.
A big reason for this is that Singapore has one of the highest vaccination rates in the world. To further analyse the efficacy of different vaccines, the study selected more than 2.7 million Singaporeans over the age of 20 who received two doses of the two doses from the "Delta period" from 1 October to 21 November 2021.
Of the approximately 2.7 million people, 74% were vaccinated with BNT162b2, while another 2% and 1% were vaccinated with CoronaVac and BBIBP-CorV, respectively. After making a comprehensive adjustment to variables such as age, sex, ethnicity, residency, socioeconomic status, timing of vaccination, etc., the researchers found that:
If the risk of contracting COVID-19 after receiving two doses of BNT162b2mRNA vaccine is set at 1, the risk of mRNA-1273 vaccine, CoronaVac vaccine and BBIBP-CorV vaccine is 0.86, 2.46 and 1.85, respectively;
If the risk of severe COVID-19 infection after receiving two doses of BNT162b2mRNA vaccine is also 1, the risk of the other three groups is 0.42, 4.59 and 1.58, respectively.
This means that the two doses of BNT162b2 are assumed to have a 90% protection against severe COVID-19, while mRNA-1273, CoronaVac and BBIBP-CorV are 96%, 54%, and 84%, respectively, the researchers said.
Table 1: Comparison of the efficacy of the four vaccines
This result is quite different from the study published by the University of Hong Kong researchers on the preprint platform medRxiv on March 22, combined with real-world data from the fifth wave of the epidemic in Hong Kong, when the University of Hong Kong concluded that the two doses of BNT162b2 vaccine and CoronaVac vaccine were 95.2% and 89.6% and 72.2% of the two doses of BNT162b2 vaccine and CoronaVac vaccine were 95.2% and 89.6% and 72.2% of people aged 20-60 and over.
But on April 1, another million-person real-world study by Brazilian researchers published on the preprint platform medRxiv came to a similar conclusion, stating that 180 days after receiving two doses of coronaVac, the effectiveness of preventing infection with the Omilkeron strain was 8.1 percent effective and 56.8 percent in critical care protection. After 8 to 59 days of homologous intensive injections, critical protective power rose to 71.3%.
Based on this latest real-world data from Singapore, the Singapore researchers suggested in the paper that only those who were not suitable for mRNA vaccination for medical reasons should adopt an inactivated vaccine alternative vaccination program, and that only 3 doses of coronaVac vaccine be considered "basic vaccination".
Optimizing vaccines and promoting vaccination of the elderly "cannot be delayed"
The results of this study may also be expected.
In principle, Lu Mengji, a German-Chinese virologist and professor at the Institute of Virology at the University of Essen School of Medicine, told the "medical community" that as the virus continues to mutate, antibody-dependent immune protection will eventually fail, and the key to building a vaccine defense line lies in the vaccine to stimulate a variety of immune responses.
mRNA vaccines and viral vector vaccines have great advantages in stimulating cellular immunity, among which mRNA vaccines are the best, and the disadvantage of viral vector vaccines is that the antibody titers produced are relatively low. The main function of inactivated vaccines is to stimulate antibodies, and there will be great problems in the face of viral mutations.
Virology expert Chang Rongshan said that the current inactivated vaccine is based on ancestral wild-type strains, and the protective effect further declines as the antigenic determinants of mutant strains change greatly. "The mRNA vaccine uses the synthetic function of the cell to guide the synthesis of S protein, not the denatured S protein in the inactivated vaccine, and the closer the protein antigen to the natural state, the more effective it can stimulate the immune system."
It may be based on this that the renewal of indigenous inactivated vaccines is also accelerating.
On March 19, the joint prevention and control mechanism of the State Council held a press conference, and Zheng Zhongwei, head of the vaccine research and development working group of the scientific research group, revealed that the local inactivated vaccine has been carried out in unit price, as well as the delta + Omicron bivalent, as well as the prototype strain + Delta + Omicron trivalent vaccine research and development work, has basically completed the preclinical research, and has been verified by production.
In addition to calling for the need to accelerate the introduction of mRNA vaccines and take into account the development and optimization of local new crown vaccines, many experts have previously told the "medical community" that the vaccination process of the elderly group has been "urgent".
Multi-country outbreak data show that the Threat of the Olmikeron strain to young people is further reduced, but it still causes a large number of deaths in the elderly and immunodeficient populations, and vaccines are one of the most powerful weapons to reverse the trend.
According to Singapore's Ministry of Health, from May 21 last year to March 15 this year, none of the people under the age of 40 in Singapore who were vaccinated throughout the vaccine died. Among the 60- to 69-year-old group, the number of unvaccinated deaths was 12.5 and 83 times higher than among those who received two doses of the vaccine and the booster.
Table 2: Proportion of COVID-19 deaths in Singapore at different ages and under different vaccination conditions
On March 15, the National Health Commission said that the risk of severe illness and death from the new crown virus in the elderly is much higher than that of young people. On the mainland, there are still 52 million elderly people over the age of 60 who have not completed the whole process of vaccination, of which 50.7% of the people over the age of 80 have completed the whole process of vaccination, and only 19.7% have completed the enhanced immunization.
The "medical community" survey found that unlike overseas, because most of the local epidemics were spread in local areas, the scale was small and was controlled in about a month, the vaccination of the elderly did not have too strong a "sense of urgency", and the domestic COVID-19 vaccination rate was roughly negatively correlated with the rise of age.
With the further increase in the spread of the Aomi Kerong mutant strain, Chang Rongshan believes that in the long run, in large cities with high population density, the extension of the new crown infection chain to the elderly group cannot be completely eliminated.
Next, how to further improve the effectiveness of vaccines and accelerate the vaccination of the elderly group has become one of the keys to breaking the new crown epidemic.
bibliography:
1: 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
2: Comparative Effectiveness of mRNA and Inactivated Whole Virus Vaccines against COVID-19 Infection and Severe Diseasein Singapore，https://pubmed.ncbi.nlm.nih.gov/35412612/#affiliation-5
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