Preliminary data on India’s nasal vaccine is promising but not enough for us to cheer. In fact, the spray vaccine is safe and induces the production of antibodies but we do not yet know if it is able to prevent contagion.
A spray vaccine against Covid? Just let it work
by Roberta Villa
Since the beginning of the pandemic we have tried in every way to achieve the much-needed herd immunity, i.e. that situation in which a sufficient number of individuals are immune to Sars-CoV2 at the same time, thus preventing viral circulation. The vaccines developed so far have been fundamental in reducing the number of deaths and hospitalizations but unfortunately they have a modest impact on reducing the number of infections.
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Why haven’t we achieved herd immunity?
- The antibodies produced thanks to healing or the vaccine do not prevent contagion and decrease over time
- Sars-CoV2 mutates a lot
Will spray vaccines help us achieve herd immunity?
Obviously we don’t know the answer to this question but theoretically spray vaccines could bring us closer to herd immunity. In fact these vaccines create a sort of protective barrier along the entry doors of the virus, i.e. mouth and nose.
Thanks to their route of administration (nasal or pharyngeal), spray vaccines induce the production of specific antibodies called mucosal IgA, this particular class of antibodies is specialized in counteracting the entry of pathogens through the mucous membranes.
The classic vaccines that we can define as ‘systemic’ induce the production of many IgG antibodies which, however, circulate in the blood and, if necessary, can reach the organs affected by the infection.
Several companies are currently developing or testing anti-Covid19 vaccines in spray format, only Bharat Biotech (India) and CanSino (China) have obtained authorization from their respective governments for distribution to the population.
Unfortunately the Chinese data are not available and even if they were they would be difficult to apply to the West where we have used different vaccines.
Last week, however, a report on the safety and immunogenicity of the iNCOVAC vaccine produced by the Indian company Bharat Biotech. In the study, the researchers focused on the safety and immunogenicity of the Indian spray vaccine.
The report shows that the Indian vaccine is very safe and induces a large amount of neutralizing antibodies and T lymphocytes. These data are very encouraging but tell us nothing about the vaccine‘s ability to prevent death, hospitalization, severe disease, but above all contagion.
We’re hoping for some real-world data to come out in the coming weeks – real world data – who can answer these questions.
Why don’t we have a spray vaccine against Covid yet?
by Aureliano Stingi
TAKE HOME MESSAGE
- To stop the Covid19 pandemic we should achieve herd immunity, i.e. a situation where no infections occur in the population
- Herd immunity is difficult to achieve because Sars-CoV2 mutates a lot and antibodies reduce the contagion but do not prevent it
- Spray vaccines promise to create a barrier in the mucous membranes that prevents contagion
- Bharat Biotech has published preliminary data on the spray vaccine that are very encouraging but say little about the real impact of the vaccine
Aureliano Stingi, doctor in molecular biology works in the field of precision oncology. He collaborates with the World Health Organization in the battle against Covid19-themed fake news
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