Could new COVID-19 vaccines, in the form of nose drops, achieve sterilizing immunity?

09/08/2022 at 07:38

EST

There is not enough data yet, but scientists are hopeful that these mucosal vaccines will prevent even mild cases of disease by achieving what is known as sterilizing immunity.

As much as it seems that the pandemic is already history and that COVID-19 has become a less serious disease, the truth is that it continues to kill thousands of people in the world. Dozens and dozens every week in Spain.

And although reliable statistics have not been made public, all experts and health professionals agree that most of the deaths are unvaccinated people.

That’s why so many research groups are still working on a way to make vaccination easier and more affordable.

And that is why there are many who are also looking for new types of inoculation. Above all to avoid the generalized rejection of injections.

An inhaled version of the vaccine approved

In this context, research is opening an important path to find vaccines that are administered as a spray for the nose or drops or pills for the mouth.

Just this week, an inhaled version of a COVID-19 vaccine, produced by the company CanSino Biologics in Tianjin, has just been approved for use as a booster dose in China.

But this is just one of more than 100 oral or nasal vaccines being developed around the world.

Mucous vaccines COVID-19, a hope for the future in the short term | FRANK MERIÑO

Could we finally be talking about sterilizing vaccines?

One of the most important contributions that these vaccines could have is the possibility of quickly stopping the virus, even before it spreads.

They would achieve it by “putting” immune cells in the thin mucous membranes that line the cavities of the nose and mouth, where SARS-CoV-2 enters the body.

And while there isn’t enough data yet, scientists are hopeful that they will prevent even mild cases of illness and block transmission to other people, achieving what’s known as sterilizing immunity.

So far, animal evidence supports the idea that sterilizing immunity against COVID-19 can be induced, but there is not yet enough human data to substantiate that claim.

In any case, it is worth trying to understand how this great advance would work in the fight against COVID-19, and the prestigious journal Nature publishes an article explaining what these new discoveries mean.

Why might mucosal vaccines be more effective?

The best way to explain it begins by remembering how the vaccines that almost all of us have injected work and that although they reduce severity and prevent hospitalization… they do not block mild disease or prevent contagion.

One of the main reasons, according to Nature, could be that they are injected into the muscle. And he explains:

Intramuscular injections elicit an immune response that includes:

  • T cells, which destroy infected cells
  • B cells, which produce antibodies that “neutralize” pathogens, binding to them to prevent them from entering healthy cells.

But these cells and antibodies circulating through the bloodstream do not reach the nose and lungs fast enough. In the time it takes to travel there, the virus spreads and the infected person falls ill.

With this new version, however, mucosal vaccines can also activate immune cells in the mucosal tissue of the nose and airways.

And as Benjamin Goldman-Israelow, a medical scientist at the Yale School of Medicine in New Haven, says, and the journal Nature itself collects:

  • “These localized cells act as sentinels at the site of infection and can act much faster.”
Iran gave its emergency approval to the vaccine in October 2021, and at least five million doses have been delivered |

How are the new vaccines?

Researchers are testing mucosal vaccines as first doses for unvaccinated people and as boosters for those who have already received COVID-19 vaccines.

Some mucosal vaccines are identical to injected vaccines, the only difference being that they are administered as liquid or drops through the nose.

This would be the case, for example, of the CanSino vaccine, recently approved in China.

It is the same as the injected version, but it is packaged in aerosols and is inhaled through the mouth with a nebulizer at one-fifth the dose of the injected version.

Some that are taken in pill form are also in development.

Are there already other mucosal vaccines?

Some mucosal vaccines are already approved for other diseases, including a spray vaccine against the flu.

There are at least nine mucosal vaccines approved for use in people, against pathogens including poliovirus, influenza, and cholera.

Eight of these vaccines are taken orally and one, which is against the flu, is administered intranasally.

The oral polio vaccine, which induces immunity in the gut, is highly successful and comes close to achieving sterilizing immunity. However, in rare cases, this live attenuated vaccine mutates and causes disease.

But mucosal vaccines have not always been so successful.

Sometimes because they fail to generate a strong enough immune response.

At other times, because it triggers side effects.

The latter would be the case of Berna Biotech’s intranasal flu vaccine. The Swiss company withdrew it from the market in 2001, after discovering that it increased the risk of temporary facial paralysis.

A less hopeful precedent

There is no doubt that there is more positive than negative news about mucosal vaccines. But there is a reality that casts a small shadow of doubt on what may happen.

It is FluMist, a live attenuated intranasal flu vaccine that is approved in the United States and Europe. And that it is proven that it outperforms the intramuscular version, especially in young children.

Even adults may also find it more convenient to “take” a vaccine through the nose, instead of injecting it.

But FluMist hasn’t worked as well with them.

The reason is believed to be because the contacts that adults have had during their lives with the flu viruses it may have caused them to develop some immunity. And that could block the attenuated vaccine from infecting nasal cells, or even kill it before it has a chance to do its job.

The question now is that researchers don’t yet know if this problem could also affect intranasal COVID-19 vaccines.

Will they be available soon?

According to Airfinity, a health analytics company in London, around 100 mucosal COVID-19 vaccines are in development around the world.

Around 20 of them are already in the phase of clinical trials in humans.

Of these, at least four, one in India, one in Iran and two in China, are already testing their safety and results compared to other vaccines.

Iran gave its emergency approval to the vaccine in October 2021, and at least five million doses have been delivered to the Health Ministry. But the institute has not yet published data on its efficacy in humans.

Russia is also said to have approved a mucosal vaccine for its market, but has not published data.

In any case, mucosal vaccines against COVID-19 are hopeful news that will hopefully be confirmed.

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