"Nature" depth: Does the new crown vaccine need a third shot?

Last week, the U.

Earlier this month, an in-depth article in the journal Nature discussed the topic of the third shot vaccine

What can the third shot of vaccine do?

Before talking about what the third shot of the vaccine can do, we must first know what the vaccine can do

This in-depth report in Nature interviewed several scientists and invited them to talk about everything about the third shot vaccine

We mentioned earlier that when the body is exposed to the new coronavirus again, the memory B cells will be quickly mobilized to promote the production of antibodies

Professor Ellebedy mentioned that with the enhancement of the third needle or even more needles, the level of memory B cells and antibody levels in the human body will not increase indefinitely, but will eventually enter a plateau

Is there evidence to support this?

Many clinical trials of the new crown vaccine have shown that the third shot of the vaccine can at least significantly increase the level of neutralizing antibodies

For the currently popular Delta (Delta) variant, the third dose of vaccine can increase the neutralizing antibody titer by more than 5 times in adults aged 18-55

▲The third dose of vaccine significantly improved the neutralization of wild-type virus (green) and Beta variants (orange) in both adults (18-55 years old, left picture) and elderly (65-80 years old, right picture) groups Antibody titer (picture source: reference [2])

Coincidentally, in early August, Moderna also mentioned in its second-quarter financial report that after 6-8 months after its mRNA completion of the second dose of vaccination, although the level of neutralizing antibodies dropped significantly, after the third dose of vaccination , The level of neutralizing antibodies can be increased by 30-40 times, exceeding the level one month after just two doses of vaccine

And in terms of safety, the third dose of vaccination will not bring additional safety issues

In a paper published last week in the New England Journal of Medicine, researchers also obtained valuable data on people with weakened immune systems

Taken together, these results provide convincing evidence that the third dose of vaccine can indeed "enhance" the immune response against the new crown

Vaccine effectiveness will always decrease.

"There is no vaccine whose antibody titers and T cell titers will not decrease over time," Professor Rafi Ahmed, an immunologist at Emory University, mentioned in this article in Nature.

In a variety of new crown vaccines, we have also seen a decline in antibody levels

For example, in a paper published online in "Science" last week, scientists found that half a year after the second injection of Moderna's mRNA vaccine, although the antibody titers weakened over time, the vaccine-induced antibody pairs included delta variants.
The six new crown variants included still have the ability to combine and neutralize
.

▲The ability of the serum to neutralize the virus and bind the spike protein persists within 6 months after the two doses of vaccine (picture source: reference [3])

The key point is that scientists don't know the "magic number" that makes vaccines ineffective
.
How much should the level of neutralizing antibody be lower before it loses its due protective power? With this number still a mystery, it is difficult to tell whether people need a third dose of vaccination
.
Once this number is known, scientists can infer whether and when a third shot is needed
.

The earlier the vaccination, the worse the resistance?

Since this magic number cannot be found, scientists can only find the answer in the real world
.
Not long ago, a study involving more than 30,000 people in Israel showed that over time and the decline in antibody levels, the proportion of new crown infections will increase significantly
.

Specifically, the researchers divided these 30,000 people into two groups.
One group was vaccinated earlier, and it took more than 146 days to receive nucleic acid testing after the second shot
.
The other group was vaccinated late and received nucleic acid testing within 146 days after the second shot
.

▲The proportion of groups who received a positive result more than 146 days between the second dose of vaccine and the nucleic acid test (picture source: reference [4])

Nucleic acid test results found 608 positive
.
What is interesting is that no matter what age group, people who have been vaccinated for a long time have a significantly higher infection rate
.
This study seems to indicate that after a long time of vaccination, the resistance against the new crown will indeed decrease
.

Another study from Israel analyzed data on more than 1.
3 million people who were vaccinated between January and April this year
.
It was found that compared with the group vaccinated in March and April, the group vaccinated in January and February had a 53% higher probability of positive for the new crown
.
Of course, this analysis does not reveal the full picture of the incident.
For example, individuals who were vaccinated early are more likely to be medical staff, and their risk of contracting the new crown itself is also higher
.

What do we want vaccines for?

At the beginning of the new crown vaccine, excellent data made the public feel that after vaccination, the risk of infection with the new crown can be completely avoided
.
Such high expectations are actually irrational
.
Even in clinical trials, the data shows that it cannot be 100% prevented from being infected with the new crown virus, not to mention the current emergence of new crown variants, its transmission power has been significantly improved
.

Therefore, the infection of the new crown after vaccination does not mean the end of the world
.
The well-known scholar Professor Eric Topol also pointed out that even if the more spreading delta variant became the global mainstream, only 2.
4% of the positive cases appeared in the population vaccinated 5 months ago, which itself shows a large scale.
The effect of vaccination
.

What's more, the protective effect of vaccines is not only to prevent infection
.
From the point of view of effectiveness, the biggest effect of vaccines is to reduce hospitalizations and deaths, followed by reducing the emergence of diseases, and finally reducing infections
.
If you are infected, you don't necessarily get sick (such as asymptomatic infection), or if your condition is not serious after getting sick (no need to be hospitalized), it is actually a great protection
.

▲Compared with the vaccinated group (blue), the unvaccinated group (green) has a much higher risk of infection, hospitalization, and death (picture source: reference [5])

This is supported by many current clinical data
.
Whether in the UK or in Israel, data shows that vaccines from Pfizer/BioNTech and Moderna can provide very good protection against severe illness
.
Even half a year after vaccination, the protective effect against severe COVID-19 can still reach more than 90%
.

The article in "Nature" pointed out that the new crown vaccine was developed for this purpose to a large extent
.

What do the experts think?

In summary, for most people, two shots of vaccine can still bring sufficient protection
.
It may not be enough to protect people from the new crown infection, but it can largely avoid the occurrence of severe illness
.
Therefore, some experts pointed out that if the third shot is inoculated on this basis, the effect can only be said to be icing on the cake, not charcoal in snow
.

As for the third booster needle, people expect it to further reduce virus infection
.
But from the perspective of global anti-epidemic, this approach may not be so reasonable
.
Infectious disease expert Professor Laith Jamal Abu-Raddad mentioned that when someone in the world has not received the first shot, healthy people like him should not get the booster shot
.
He pointed out that our main purpose is to "make more people get the first shot
.
"

Other experts said that for high-risk groups, the third shot can be considered because "the risk is small and the benefit is great
.
"

Note: The original text has been deleted

Reference materials:

[1] COVID vaccine boosters: the most important questions, Retrieved August 14, 2021, from https:// Second Quarter 2021 Earnings Teleconference.
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pdf

[3] Amarendra Pegu et al.
, (2021) Durability of mRNA-1273 vaccine–induced antibodies against SARS-CoV-2 variants.
Science Doi: 10.
1126/science.
abj4176

[4] Israel et al.
, (2021).
Elapsed time since BNT162b2 vaccine and risk of SARS CoV-2 infection in a large cohort.
medRxiv, https://doi.
org/10.
1101/2021.
08.
03.
21261496

[5] Improving communications around vaccine breakthrough and vaccine effectiveness.
Retrieved August 1, 2021, from https://context-cdn.
washingtonpost.
com/notes/prod/default/documents/54f57708-a529-4a33-9a44-b66d719070d9/note /753667d6-8c61-495f-b669-5308f2827155.