Covid Vaccine Update: Nasal Vaccines a Sniffing Hope
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Covid Vaccine Update
Nasal Vaccines—Sniffing Hope
World seems to be moving towards centuries old technique of Sniffing Vaccines. In 18th Century Smallpox scab crushed powder used to be blown in nose as vaccine. Old seems to be turning Gold.
Two needle-free COVID-19 vaccines have been approved for use in China and India on the 5th and 6th of September 2022, respectively. Let's analyse
Why are nasal vaccines necessary?
Both involve the use of a vaccination technology hitherto not popular in humans. China's vaccine is inhaled by Nebulization through the mouth and nose as an aerosol, while the Bharat Biotech vaccine is instilled as nasal drops.
Both are designed to target the mucus membrane right where the SARS CoV -2 land –the Nasal Mucosa. They are purported to stimulate the formation of local IgA antibodies that coat the mucus membranes and entrap and neutralise the Covid-19 Virus. Thus, they can stop the virus from replicating at its entry and spreading to the lungs and other parts of the body. Scientists feel that mucosal vaccines might successfully prevent mild illnesses and block transmission to other people.
Are there any mucosal vaccines already approved against Covid?
Yes. Iran and Russia have already approved mucosal vaccines developed in their countries. RAZI Vaccine is already in use in Iran. Nearly 5000 doses have been used so far in Iran.
How many more are in development?
More than 100 mucosal vaccines against the disease are in development globally, and about 20 have reached clinical trials in humans.
CanSino Biologics, Tianjin developed China's inhaled vaccine and named it 'Convidecia Air'.
It is also called Ad5-nCoV. This vaccine has the same ingredients as the company's COVID-19 injectable vaccine Ad5-nCoV available for more than a year. But the new avtar Convidecia Air' comes in a nebulisable solution. This revised version has been approved to be used as a booster dose. Phase II study published in medRxive showed that aerosolized Ad5-nCoV following two-dose injectable CoronaVac was more immunogenic than three-doses of injectable CoronaVac. It is noteworthy that Corona Vac is the most commonly used vaccine in China and is based on a killed virus vaccine platform. In addition, the vaccine used as a booster showed detectable Nab antibodies against omicron.
However, there is a caveat: the immune responses produced by the inhaled vaccine wane over time.
It is noteworthy that CanSino's initial one-shot injectable vaccine was 66% effective in preventing Covid-19 symptoms and 91% effective against severe disease.
India's Nasal Vaccine:
India's vaccine, called iNCOVACC, developed by Bharat Biotech, has been approved as a two-dose primary inoculation for adults more than 18 years rather than a booster. However, the vaccine has also shown efficacy as a booster in trials (unpublished reports).
Bharat Biotech's ChAd36-SARS-CoV-S COVID-19 vaccine is a (Chimpanzee Adenovirus Vectored) recombinant nasal vaccine. The vaccine has been developed in collaboration with the University of Washington, St Luis.
As per Bharat Biotech, the intra-nasal vaccine stimulates a broad immune response – neutralizing IgG, mucosal IgA, and T Cell responses.
Two separate but simultaneous clinical trials were done to evaluate BBV154 as a primary 2- dose schedule; and a heterologous booster dose for subjects who have previously received 2 doses of the two covid vaccines( Covaxin and Covishield) in India.
Both trials were declared successful by the company. But trial data is still not in the public domain.
What are the Phase III trial results?
None of the companies has released Phase III trial data to the Public.
How successful will nasal vaccines be?
It is challenging to answer presently. But one should not have very high expectations. After all, even the live virus instilled in the nose could not produce disease in more than 56% of people. So expecting a vaccine to stop transmission of a virus or prevent even mild illness — achieving what is called sterilizing immunity — is a very high bar.
How long will the immunity persist?
IgA antibodies are prone to get washed in nasal secretions. How long they will stay and how quickly T cell responses take over is a matter of speculation. Nevertheless, as the incubation period of evolving variants is decreasing (Alpha 5 days, Delta 4.4 days, and Omicron 3.4 days) and T cell responses may take time to get hooked up and respond, the mucosal immunity might play a crucial role in the initial days.
What is the experience with the Nasal vaccine used so far?
Two other mucosal COVID-19 vaccines already approved so far have published little data. First, a nasal spray made by Razi Vaccine was approved in Iran against COVID-19 in October 2021. Till now, nearly 5000 doses have been used.
And Russia's health ministry is reported to have approved an intranasal spray version of Sputnik V; the country's injected COVID-19 vaccine.
Mucosal vaccines available against other Diseases:
Mucosal vaccines have been developed and used for other diseases, including poliovirus, influenza, and cholera. Most of these vaccines are taken orally, but one, against flu, FluMist, is administered through the nose but is not very popular.
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