ByCan a virus be wiped out of the globe?
An inspiring example stands out -Polio. It is no secret that polio was driven out of the World using a potent oral polio vaccine because it attacked the virus right at its portal of entry. Polio vaccine immobilized the virus in its favourable replication environment –the gut.
In the case of Corona, researchers and scientists have been struggling hard to take hold of the nasal cavity to defeat Corona Virus. More than 100 mucosal vaccines are in the fray. Some are already out for use.
How do mucosal vaccines work?
Theoretically, these vaccines prime immune cells in the mucous membranes lining the nose and mouth (the entry points of SARS-CoV-2) and quickly stop the virus — before it spreads. Mucosal vaccines block transmission and prevent even mild illness achieving what’s known as sterilizing immunity.
Are there any examples of successful nasal vaccines till now?
Flumist– nasal spray vaccine containing weakened flu viruses. The vaccine works well in children but doesn’t stand out as potent for adults because antibodies accumulated in adults against the flu virus by repeated flu infections render the vaccine ineffective before it can even act. The nasal mucosa is a highly intelligent sentry studded with IgA immunity, which entraps and blocks any unfriendly pathogens.
To dodge the nasal sentinel, researchers send SARS-CoV-2 spike protein (gene) to nasal mucosa encrypted in a nasal-friendly pathogen. Hence, Vector-based vaccines find favours for the purpose. AstraZeneca’s intramuscular COVID shots belong to the same group of immunizations.
◆Bharat Biotech’s nose-drop concoction also belongs to this category, and so are China’s two mucosal vaccines, as well as the nasal version of Russia’s Sputnik V shot.
◆Other researchers are making vaccines containing ready-made coronavirus spike protein, akin to the Parenteral Novavax vaccine. Among them already in use is Iran’s mucosal COVID vaccine, Razi, which has been used in a few million doses. But details of immunity have not been shared till now.
◆A newer, still-in-pipeline vaccine candidate from the immunologist Akiko Iwasaki and her colleagues at Yale University also belong to this category.
◆The Yale group is also testing an mRNA-based nasal recipe.
◆And Vaxart company has been tinkering with a COVID-vaccine pill that could be swallowed to provoke immune cells in the gut, which would then deploy fighters throughout the body’s mucosal surfaces, up through the nose. Vaxart has already begun Phase II trials of its oral vaccine for Covid.
Developing nasal vaccines is a much bigger challenge than intramuscular vaccines as not all succeed.
Intranasal version of the AstraZeneca vaccine was found highly effective in animals, but it hardly triggered any immune response in humans, even when tried as a booster after Intramuscular shot into an early human trial–published in Lancet last month.
But there is a silver lining too…
The mucosal COVID vaccines from India have shown promising results in early human trials.
Bharat Biotech’s —inCoVacc, intranasal Covid Vaccine -the name itself is music to ears. It stimulates a broad immune response – neutralizing IgG, mucosal IgA, and T cell responses at the site of infection (in the nasal mucosa) – essential for blocking both infection and transmission of COVID-19. It is to be instilled 4 Drops in each nostril.
The Drugs Controller General of India cleared it in September 2022, and in November 2022 vaccine was approved for primary vaccination of adults over 18 years. Now the nasal drop vaccine has been released as a booster in adults.
Anyone who has completed primary COVID-19 vaccination with either Covaxin or Covishield can opt for heterologous prime-boost using inCoVacc after registration on the Cowin portal.
The vaccine is available as a Single/Double Dose liquid formulation of 0.5ml/1ml. Four drops are to be instilled in either nostril using the dropper provided.
*Dr. Satish K Gupta is an MD in Medicines, a Visiting Senior Consultant Physician and Internist at Max Super Speciality Hospital, and a Clinical Assistant Professor at GS Medical College, Chaudhary Charan Singh University, Meerut. He is the author of Journey of COVID in India: A Doctor’s Perspective.
