mRNA or inactivated COVID-19 vaccine: Which one is better?

mRNA or inactivated COVID-19 vaccine: Which one is better?  There are two main types of COVID-19 vaccines currently available in the world:

• Inactivated vaccine:  China SINOPHARM, KEXING (SINOVAC)
• mRNA vaccine: mainly developed by Pfizer, Moderna, BioNtech, Fosun

If vaccination is required, should I choose mRNA vaccines or inactivated vaccines? What are the advantages and disadvantages?

The development history of the two vaccines

Inactivated vaccines are the most traditional classic technical route for vaccine preparation, that is, culturing and inactivating viruses in vitro to make them non-toxic. But the “corpses” of these viruses can still stimulate the body to produce antibodies, so that immune cells can remember what the virus looks like.

The earliest “vaccine” can be traced back to the 16th century. In order to prevent smallpox during the Longqing period of the Ming Dynasty, ancient Chinese medical scientists pulverized the skin crusts of smallpox patients after recovery and blown them into the nasal cavity of unaffected children.

The “grinding of skin crusts into powder” of recovered patients is actually a process of virus inactivation as we now think, but it is not ruled out that this method will still retain some live viruses, which is dangerous. However, at that time, this method greatly reduced the mortality rate of vaccinia populations, so it spread from China to Asian and European countries, and in 1772 it became the official vaccination method allowed by the British royal family.

After being spread to the United Kingdom, a British doctor discovered that the milkmaid would no longer be infected with smallpox after contacting cows with vaccinia. He became curious, why did the milking women’s union develop such immunity? So he started to vaccinate 24 volunteers with “vaccinia” to see if it could prevent smallpox, and it was successful.

The root of “vacca” in the English word “vaccine” for vaccines today refers to cow in Latin, and this British doctor is Edward Jenner (Edward Jenner). In 1796, the smallpox vaccine he invented was the world’s first vaccine, and he was therefore called the father of immunology.

In 1881, French scientist Louis Pasteur set out to study rabies.

Rabies is a zoonotic disease caused by the rabies virus. The virus can multiply in the salivary glands of dogs and cats. After biting a person, the residual saliva from the wound can infect people. In the absence of a vaccine at that time, the main manifestations of people’s illness were excitement, breathing difficulties and progressive paralysis. Once bitten by a rabies dog, the mortality rate was nearly 100%.

In 1885, Pasteur developed an attenuated rabies vaccine in an attenuated way. His reputation drew help from across the Atlantic. At that time, several boys in New Jersey, USA, were attacked by dogs infected with rabies and were dying.

This news aroused the attention of the American people, who spontaneously raised funds to help these boys cross the Atlantic Ocean to Paris to seek help from Pasteur, and Pasteur did not live up to expectations. Using his rabies vaccine, he successfully treated a rabies case. 9-year-old child bitten. So there is the rabies vaccine that we still use today.

It can be seen that inactivated vaccines are a traditional vaccine preparation method with a long history. Most of the vaccines we have vaccinated today are prepared in the form of inactivated viruses, such as DPT and hepatitis A vaccines.

However, the main problem with inactivated vaccines is the large vaccination dose. For emerging viruses, it is difficult for the output of vaccines to keep up with the speed of virus mutation. Therefore, mRNA vaccines are in sharp contrast with inactivated virus vaccines due to their fast production speed and simpler technology. The history of its development has been introduced in the previous article. See the ten-year history of RNA vaccines.

Comparison of the protective effects of the two types of vaccines

Sinopharm stated that the safety of the inactivated vaccine is good after vaccination, and the effectiveness of the protection against the new coronavirus is about 79%. Although it is lower than the 95% of the RNA vaccine phase III clinical trial data, this may be due to the form of inactivated virus. The immune protection induced by it is weaker.

Since COVID-19 will continue to mutate as it spreads, and the existing vaccine is developed based on the characteristics of the virus before the mutation, it may face the situation that even if it is vaccinated, it cannot avoid the infection of the mutant virus. At present, the three mutant new coronavirus strains that have caused widespread concern are: the British mutant new coronavirus strain B1.1.7, the South African mutant new coronavirus strain B.1.351, and the Brazilian mutant P.1.

• British variant strain: B1.1.7, originated in September 2020, became the most common strain in the UK, with a transmissibility 40-70% higher than the previous virus.
• South Africa variant strain: B.1.351, originated in December 2020, South Africa is mainly infected with the virus strain. The spread is fast and the spread is high.
• The Brazilian variant strain: P.1, originated from tourists from Brazil found during a Japanese airport inspection in January 2021. The current impact on infectivity and pathogenicity is unknown.

According to current research data, individuals after Pfizer’s mRNA vaccination still have the ability to neutralize the British variant. Research shows that the individual’s serum after vaccination has no obvious downward trend in the protection of the British new coronavirus. The protective effect remains to be seen.

In terms of domestically-made inactivated vaccines, the research led by Academician Gao Fu of the National Center for Disease Control and Prevention found that the neutralizing effect of the inactivated vaccines on the South African variant strain decreased slightly, but overall it would not significantly affect the protective effect after injection.

Therefore, for the current new coronavirus mutant, the protective effects of the two vaccines have not been significantly reduced, but the research to optimize the vaccine is also in progress.

Data disclosure of the two vaccines

Regarding the data of domestic vaccines, whether it is from pre-clinical animal experiments or clinical phase III trial data to measure the important effects of vaccines, they are far less detailed than foreign mRNA vaccine data. for example:

The indicator for evaluating the effectiveness of vaccines must be the protection rate in the real world. For example, now everyone’s eyes are focused on Israel. Israel analyzed the incidence of COVID-19 among 2.6 million people in the real world, which is a large-scale Phase IV clinical trial. The validity of the 95% data on the protective effect of Pfizer’s vaccine phase III clinical trial was verified.

However, because the real world is extremely complicated and there are many restrictive measures to interfere, the evaluation process of clinical phase IV is very difficult. Regardless of Phase IV clinical trials, the protection rate of Phase III clinical trials is the gold standard for evaluating vaccine effectiveness and the main decisive factor in whether it can be marketed.

Both Pfizer and Moderna clearly listed the clinical Phase III data of 30,000 to 40,000 people in the reports submitted to the FDA for approval; however, due to better domestic epidemic control, domestic inactivated vaccines can only be used for clinical phase III in many overseas countries. In the interim trials, due to the complexity of integrating data, the overall progress is slow, and there is currently no data clearly disclosed.

As far as the current research data is concerned, the two RNA vaccines in the United States are relatively transparent and open, so experts from all walks of life can discuss and interpret them at any time, and they have also published countless very meaningful opinion articles during the period. Although clinical trials in other countries are slowly advancing, the previous data disclosures are relatively small and there is a lack of valuable discussion and analysis.

Vaccinations for pregnant and breastfeeding women

Pfizer and Moderna did not include pregnant women and breastfeeding women in clinical trials, so some people questioned the safety of mRNA vaccines for pregnant women. There is a rumor in Europe and the United States that after the mRNA vaccine is administered, the antibodies produced in the body can not only bind to the new coronavirus S protein, but also an embryonic protein (syncytin-1). Therefore, the antibodies produced by the vaccine will attack the embryo, thereby Cause women’s miscarriage or infertility.

In response to the rumor, Professor Iwasaki of Yale University compared the amino acid sequence of the COVID-19 virus dendritic protein and the so-called embryonic protein syncytin-1 and found that they did not have obvious similarities; animal experiments did not see the effect of the vaccine on pregnancy; Analysis of the serum of women infected with the new coronavirus did not detect antibodies that can react to synctin-1.

In the clinical data, there are no reports of infertility in women after vaccination. On the contrary, there are cases of successful pregnancy in women after vaccination.

Due to the lack of experimental data for pregnant women, for pregnant women, whether or not to vaccinate should depend on the female virus exposure probability. For example, if you can ensure that you have a small range of activities during pregnancy and you can maintain social isolation, then not being vaccinated can also reduce the risk of COVID-19 infection. However, if you have to be exposed to a high-risk virus due to work or other reasons, then the risk of new coronavirus infection is far greater than the potential risk of vaccination.

For breastfeeding women, although there is not enough data to disclose, the potential risk of the vaccine is greatly reduced compared to pregnant women, and its safety is almost guaranteed.

Because after the vaccine is injected into the mother’s body, not only the mother can get antibody protection, at the same time the antibodies can be passed to the baby through the milk. Some people may be worried about whether the RNA components injected into the mother’s body will also be passed to the baby through the milk? Iwasaki said that this possibility is very small, and even if a very small amount of mRNA molecules are passed to the baby through milk, it will be metabolized and degraded in the baby’s gastrointestinal tract, so there is almost no risk.

Conclusion

From the current point of view, because mRNA vaccine is a newly born technology, the application time is too short, we can not assess its potential long-term risks, so safety will definitely be a factor that everyone will focus on. But in the long run, the application of this new technology will mark us entering a new era of personalized vaccine design for individuals and populations.

(source:internet, reference only)

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