A new Singapore study compares the efficacy of a Covid-19 vaccine against 2019-nCoV infection and severe prevention, published April 12, 2022 in Clin Infect Dis. The study aimed to compare the four available vaccines in Singapore and to investigate the results of other studies showing that mRNA vaccines have higher efficacy than non-mRNA vaccines.
The four vaccines are the Pfizer-BioNTech/Comirnaty vaccine and the Moderna vaccine, which are mRNA vaccines, and the Sinovac-CoronaVacvaccine and Sinopharm vaccines, which are non-mRNA vaccines that use inactivated viruses to trigger an immune response vaccine. The Pfizer vaccine was used as a reference as it is most commonly used in Singapore.
The study looked at the incidence of Covid-19 infection and severe illness between October 1 and November 21, 2021, using an official database maintained by the Ministry of Health (MOH) in Singapore . The investigators restricted the cohort to two weeks after completing two doses of the vaccine to generate an adequate immune response, and received a second dose within 120 days of our analysis to control for weakened immunity. Separately, “serious illness” was defined as requiring supplemental oxygen in a hospital, admission to an intensive care unit, or death.
During 14 to 120 days after two doses of vaccine, 2,709,899 people were enrolled in the study cohort, of whom 2,001,181 (74%) received Pfizer BioNTech/Comirnaty and 628,012 (23%) received Moderna, 60,407 (2%) received Sinovac CoronaVac and 20,299 (1%) received Sinopharm. During the study period, 107,220 people were confirmed to be infected with COVID-19 by PCR, of whom 644 developed severe disease.
Individuals vaccinated with Sinovac-CoronaVac were more Likely to be infected (adjusted IRR 2.37; 95% CI 2.29 C 2.46) and more likely to develop severe disease (adjusted IRR 4.59; 95% CI 3.25 C 6.48); compared with Sinopharm, vaccinated with Sinopharm were also at higher risk of infection (adjusted IRR 1.62; 95% CI 1.43 C 1.85), while Moderna-vaccinated individuals had a lower risk of severe disease (adjusted IRR 0.42; 95% CI 0.25 C 0.70) compared with those Those receiving Pfizer-BioNTech/Comirnaty (Table 1).
In other words, using the Pfizer mRNA vaccine as a reference, people treated with Sinovac-CoronaVac: 2.37 more likely to be infected than those treated with Pfizer Those who received Sinopharm’s inactivated vaccine were 1.62 times more likely to be infected than those who received Pfizer; and those who received Moderna were 0.84 times more likely to be infected than those who received Pfizer. In the prevention of severe disease caused by Covid-19 infection, people treated with Sinovac-CoronaVac were 4.59 times more likely to develop severe disease than those treated with Pfizer; those treated with Sinovac, People who received Pfizer were 1.62 times more likely to develop severe disease; people who received Moderna were 0.42 times more likely to develop severe disease than those who received Pfizer.
In general, the comparison of the effects of each vaccine is Modena>Pfizer>Sinopharm>Kexing.
Individuals who received 2 doses of the inactivated whole virus vaccine were observed to have lower protection against COVID-19 infection than those who received the mRNA vaccine, according to the investigators. Nonetheless, both mRNA vaccines and inactivated whole virus vaccines provide adequate protection against severe COVID-19 disease, and vaccination remains a key strategy in the response to the pandemic. Studies such as UK COV-BOOST have shown that a third dose provides additional protection against COVID-19, and future studies should continue to monitor the effectiveness of these vaccines and assess how further booster doses enhance them.
Study concludes that “both mRNA vaccine and inactivated whole virus vaccine provide adequate protection against severe Covid-19 disease” and affirms vaccination as a ” the importance of key strategies”.
The study’s authors said in their introduction: “Our goal was to compare mRNA and inactivated whole virus vaccines in the same population, as these findings will help guide policy recommendations to prevent infection and reduce stress on the healthcare system.”
It is worth noting, however, that although this study is rigorous and has a large sample size, there are two important issues to note:
First, the study was conducted from October 1st to November 21st, 2021. During this period, Delta infection was still the main infection, not Omicron. It is necessary to conduct a comprehensive evaluation for Omicron infection. At the same time, the latest Chilean study on the protective effect of Sinovac vaccines on children during Omicron, see: Chile research report Sinovac inactivated new coronavirus vaccine in real-world effects of children infected with Omicron-MedSci.cn, via Only by making comprehensive judgments can we have a more comprehensive understanding of the role of vaccines.
Secondly, this study mainly evaluated the protective effect of two vaccine injections, and the effect of three injections was not compared. Combined with the latest results in Hong Kong, the protective effect of three inactivated vaccines on severe illness and death in the elderly is similar to that of the mRNA vaccine (Pfizer). For inactivated vaccines, the effect of three injections is far better than that of two injections; For mRNA vaccines, the effect of three injections is only limited compared to two injections. Therefore, there is also a huge difference between the effects of two needles and three needles, and more data will be needed for evaluation in the future.
References  Premikha M, Chiew CJ, Wei WE, Leo YS, Ong B, Lye DC, Lee VJ, Tan KB.Comparative Effectiveness of mRNA and Inactivated Whole Virus Vaccines against COVID -19 Infection and Severe Disease in Singapore. Clin Infect Dis. 2022 Apr 12: ciac288. Doi: 10.1093 / cid / ciac288 p>
Source: Plum Medicine p>