October 18, 2021

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mRNA COVID-19 vaccine more than 80% effective against Delta Variants.

mRNA COVID-19 vaccine more than 80% effective against Delta Variants.

mRNA COVID-19 vaccine more than 80% effective against Delta Variants



mRNA COVID-19 vaccine more than 80% effective against Delta Variants..  mRNA vaccine is still effective against delta variants



Recently, the delta mutant has spread rapidly around the world. The delta mutant strain is more infectious. Some health experts mentioned that the original concept of “close contact” is no longer applicable to this mutant virus [1]. Whether the existing COVID-19 vaccine can effectively prevent delta variants has become a public concern. A number of authoritative studies from the real world have shown that the protection rate of mRNA vaccines against delta variants is still over 80%.



1. British test negative design study: BNT162b2 mRNA vaccine has a protection rate of 88% against delta variants causing symptomatic COVID-19


The UK study published online on the NEJM on July 21[2] adopted a test-negative design method, which is about comparing the vaccination status of symptomatic COVID-19 cases with symptomatic but test-negative cases (non-COVID-19 cases). This method is helpful To reduce research bias caused by differences in patients’ medical habits, testing opportunities and diagnostic criteria.

The test negative design is a common and standardized method in real-world research on vaccine effectiveness. The study detected a sample size of 4272 Delta mutant strains. The study showed that after completing two doses of BNT162b2 mRNA vaccine, the protection rate of preventing symptomatic COVID-19 caused by the Delta mutant strain was 88%. Compared with one dose of mRNA vaccine, the two full doses of vaccine have a significantly higher protective effect against delta mutant strains (88% VS 35.6%).




2. Research in Scotland and Canada: The protection rates of mRNA vaccines against delta variants are 83% and 87%, respectively


There are other recent studies that have adopted the test-negative design method to report the effectiveness of mRNA vaccines in preventing infections by delta variants. A Scottish study [3] showed that the effective rate of preventing symptomatic COVID-19 caused by the delta variant was 83% after 14 days of vaccination with two doses of BNT162b2.

This study analyzed nearly 20,000 COVID-19 community cases and 377 hospitalized cases in Scotland. Delta variants accounted for 7,723 and 134 cases, respectively. The study also found that compared with the alpha variant, the risk of hospitalization for patients with the delta variant COVID-19 has approximately doubled, and the mRNA vaccine can reduce the risk of hospitalization. It is worth noting that the other adenovirus vaccine involved in the study is less protective than the mRNA vaccine (67% VS 88%) against the delta variant.


A study submitted by Canada on the preprint platform [4] showed that the effective rate of preventing symptomatic COVID-19 caused by the delta variant strain was 87% 7 days after 2 doses of BNT162b2 mRNA vaccination. The study also suggests that it is necessary to complete 2 shots of vaccination in order to achieve a higher protection rate.


In addition, another pre-printed study [5] showed that the protection rate of two doses of BNT162b2 mRNA vaccine to prevent hospitalization of COVID-19 caused by the delta variant strain was 96%.


4 studies show that the mRNA vaccine(BNT168b2) protects delta over 80%

The population being studiedDelta mutated strains (B.1.617.2)Published
Eingland88% with symptoms of infectionJuly 21 on NEJM
Scotland83% with symptoms of infection June 26 on Lancet
Canada87% with symptoms of infection June 28 (pre-print)
UK96% Preventive hospitalizationJune 15 (pre-print)

3. With the increase in vaccine coverage, it may highlight the increase in breakthrough infections, and relevant data should be interpreted objectively and cautiously


Existing evidence shows that BNT162b2 mRNA vaccine still has a good effect in preventing delta variant infection, especially within 6 months after the second dose. However, it is foreseeable that with the increase in vaccine coverage around the world, among the newly emerging infections and hospitalized cases, the proportion of infected people who have been vaccinated (breakthrough infection) will gradually increase, and may even exceed that of unvaccinated cases. Of the infected (as shown in the picture). In this context, the interpretation of breakthrough infection and vaccine effectiveness data should be more objective and cautious.


Schematic diagram of the change in vaccine coverage and the proportion of vaccinated or not among hospitalized patients with COVID-19

mRNA COVID-19 vaccine more than 80% effective against Delta Varants




4. What else can we do to fight against powerful mutants?


The effective rate of the vaccine may weaken over time. When should booster immunization be given to specific groups of people, there have been a number of sequential vaccination with different vaccines, and research on booster immunization is underway. Unpublished data [7] showed that a booster immunization 6 months after two doses of BNT162b2 mRNA vaccination can increase the neutralizing antibody level of subjects by 5-10 times.


In early July, the US Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) issued a joint statement[8] that at this stage, individuals who have completed the entire vaccination process do not need to be boosted.

The FDA and CDC made this decision based on existing evidence that individuals who complete the full course of vaccination can obtain effective protection against severe illness and death (including those caused by the delta variant), while almost all cases of hospitalization and death of COVID-19 pneumonia have not been reported.

Vaccination, so individuals who have not been vaccinated are encouraged to get vaccinated as soon as possible. The FDA and CDC also stated that they will continue to review emerging evidence and use booster doses of vaccination when necessary.

In an interview with CNN on July 25, Professor Dr. Fauci also mentioned: “When a booster vaccination is needed, transplant patients, cancer chemotherapy, autoimmune diseases, and immunosuppressants The patients treated may be the first to use the third dose of booster mRNA vaccine.


(source:internet, reference only)

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