July 14, 2024

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Omicron: Pfizer’s COVID-19 vaccine neutralization ability decreased by 40 times?

Omicron: Pfizer’s COVID-19 vaccine neutralization ability decreased by 40 times?


Omicron: Pfizer’s COVID-19 vaccine neutralization ability decreased by 40 times>

Omicron’s first serum neutralization result: Pfizer’s COVID-19 vaccine neutralization ability decreased by 40 times.

The author said before that due to dense mutations in Omicron’s Spike protein, it is difficult not to affect the effectiveness of the vaccine.

The earliest data on the effectiveness of vaccines should be serum neutralization tests for the purpose of detecting neutralizing antibodies.


On December 7, South African scientists provided an update in this regard. Preliminary experimental results showed that the ability of Pfizer’s vaccinators to neutralize Omicron in the serum has dropped significantly, compared with the original virus strain, by 40 times . This is far beyond the Beta strain, which had the worst immune escape before.


This result is not ideal or unexpected. However, it can be comforted that at least Omicron is not a complete immune escape .

According to the research leader, South African scientist Alex Sigal, the serum of people who have been previously infected and vaccinated can still neutralize Omicron.


Omicron: Pfizer's COVID-19 vaccine neutralization ability decreased by 40 times

Alex Sigal tweeted the conclusion of the trial


What does a 40-fold decrease mean? It is still difficult to determine. It is important to note that the research of Alex Sigal’s laboratory is only the most preliminary results, and further verification is required.


It is assumed that a 40-fold reduction is a common phenomenon-applicable to other vaccines, booster shot, serums of recovered patients, and so on.

We can try to analyze some recent vaccine serum neutralization experimental data.


Based on the data in the Phase III clinical trial of Moderna, the researchers obtained the result of modeling that after vaccination, the neutralizing antibody titer of 1000 (50% neutralizing pseudovirus) corresponds to the effectiveness of preventing symptomatic COVID-19 infection (three-month follow-up Time) is 96%, 100 corresponds to 91%, and 10 corresponds to 78% .

(Interlude, this is a neutralizing antibody, not a commercial test antibody; and it is an analysis of the average antibody level in the population, not an individual study. At this stage, any test for the COVID-19 antibody to an individual is used to predict the effectiveness, either IQ tax, or ignorance)


In the third random mixed-dose clinical trial of various vaccines recently conducted in the United Kingdom, one month after receiving two doses of Pfizer vaccine, the neutralizing antibody titer against the original virus strain was around 1800.

In fact, whether it is Pfizer or Moderna, the neutralizing antibody titer one month after the booster shot is in this range.

Taking the original virus strain neutralizing antibody 2000 as an example, the titre of neutralizing antibody will only be 50 if it is reduced by 40 times against Omicron .


Note that this is still the peak value of neutralizing antibody after the booster shot.

The peak antibody of Pfizer and Moderna after the booster shot is about 2-3 times of the peak after the second dose. Moreover, the so-called peak value, as the name implies, will gradually decrease in the future.

Judging from the clinical trial of Moderna booster shots and the mixed test of NIH, the peak of mRNA vaccine booster shots is very early, and the titers of neutralizing antibodies in 14 days are higher than the results in one month.


Such a large decrease in antibody neutralization capacity means that the booster shots that may have been expected to greatly reduce infections, in the face of Omicron, may only be able to barely maintain a certain degree of anti-infection ability -and it may be relatively short-term.


Of course, the most important role of vaccines is to protect against severe illness, which is difficult to infer from serum neutralization tests.

The titers of neutralizing antibodies of many vaccines are far from each other, but the gap in the prevention of severe illnesses is small.

In addition, over time we have observed that the neutralizing antibodies of vaccinators have dropped significantly, but the effectiveness of preventing severe illnesses has fallen far less than the effectiveness of preventing mild illnesses or infections.

There are two possible explanations. One is that prevention of severe illness may not require a lot of neutralizing antibodies, and the other is that prevention of severe illness may involve more immune responses-memory B cells, T cells, etc.


The vaccine’s ability to prevent severe Omicron disease can only wait for more data to be collected in the future.

If the existing vaccines can maintain a certain degree of ability to prevent severe illness, it is actually a good result to maintain the effectiveness of part of the prevention of infection through booster shots.

But the results of the Pfizer serum neutralization test provided by South Africa undoubtedly point to a situation that many scientists have worried before: Omicron will have a major impact on our most important cornerstone of epidemic prevention today-highly effective vaccines .


Regardless of whether it is Beta or Delta, it is not a big problem to use existing vaccines for booster shot.

Facing Omicron, existing vaccines for booster shot seem to be more and more like short-term emergency relief. Note that emergency rescue is very important and critical.

Yes, so it is necessary to inoculate with the current booster shot.


But it may be necessary to replace the vaccine against Omicron. And this still has a strong urgency.

It took only 3-4 months for Delta to spread in the United States in May and become a mainstream mutant in August -the same time span in many countries. In the current tracking results of Omicron, the speed is at least as fast as Delta.

We can only hope that the current booster shot can be exchanged for three or four months, and this time is enough for the replacement vaccine to be ready.






Omicron: Pfizer’s COVID-19 vaccine neutralization ability decreased by 40 times

(source:internet, reference only)

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