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China approves inhalable Covid-19 vaccine

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Convidecia Air uses a nebulizer to turn the liquid into an aerosol to be inhaled through the mouth

| THE INDEPENDENT | The China National Medical Products Administration (NMPA) has approved CanSino Biologics’ (CanSinoBIO) recombinant Covid-19 vaccine (adenovirus type 5 vector) for inhalation, Convidecia Air, as a booster.

This vaccine is based on the same adenovirus vector technology platform as Convidecia, the intramuscular version.

Offering a non-invasive option, Convidecia Air uses a nebulizer to convert the liquid into an aerosol to be inhaled through the mouth, the company noted.

The needle-free vaccine can also elicit full immune protection against the SARS-CoV-2 virus after a single inhalation.

In March last year, CanSinoBIO obtained the approval of clinical trial application to analyze Convidecia Air. The vaccine was developed in partnership with the Beijing Institute of Biotechnology (BIB).

According to studies, Convidecia Air could induce robust cellular, humoral and mucosal immunity to achieve triple protection as well as control virus spread and infection.

The company has currently achieved regular manufacturing of several innovative vaccines and established a worldwide supply chain to increase accessibility to quality vaccine products for people around the world.

Inhalable vaccine in trial

An inhalable version of a single-shot, adenovirus-based viral vector vaccine could provide a new option for vaccination against COVID-19.

In October 2021, the World Health Organization set a target for countries to vaccinate 70% of their population against COVID-19 by mid-2022. However, improving access and distribution of vaccines to the more than 90% of people in low-income countries who are still unvaccinated remains a challenge.

Researchers rushing to reduce the logistical and financial barriers of vaccination suggest that the development of inhalable vaccines could be a way forward.

Compared to intramuscular vaccines, which generally require low temperature storage and skilled healthcare personnel to administer them, inhalable vaccines can be administered using disposable devices, with minimal storage requirements for mass vaccination.

Inhalable vaccines can also induce a localized immune response targeting the mucosal surfaces where pathogens enter, instead of a systemic immune response, without specifically targeting the pathogen’s region of infection, as intramuscular vaccines do.

This specificity also means that only a lower dose might be needed compared to intramuscular injections.

New routes of administration

In 2021, Tianjin-based biopharmaceutical company CanSino Biologics (CanSinoBIO) completed a Phase III clinical trial of its intramuscular COVID-19 vaccine, which involved 45,000 volunteers worldwide. The vaccine was later approved for use in China, Hungary, Pakistan, Malaysia, Argentina and Mexico. CanSinoBIO is leading the development of an inhalable version of the vaccine.

CanSinoBIO’s vaccine is a recombinant viral vector vaccine, a class of vaccines that use a modified version of a different virus to deliver instructions to cells that trigger an immune response.

The adenovirus-derived viral vector, which easily infects cells but does not cause disease, serves as a carrier that delivers genetic material that codes for the SARS-CoV-2 spike protein to cells.

Once it enters a cell, the gene is transcribed to express the spike protein, which in turn serves as an antigen that stimulates the immune system to recognize the COVID-19 virus.

Zhu says the inhalable vaccine mimics how COVID-19 enters the human body through the respiratory tract. When CanSinoBIO’s vaccine is aerosolized into tiny particles, it can then be inhaled into the airways and lungs to trigger immunological memory and initiate an immune response in the mucous membranes of the airways.

When producing the inhalable vaccine, CanSinoBIO deletes the genes related to virus replication from the adenovirus type 5 vector, so the vector is defective for replication in the human body. A gene sequence encoding the SARS-CoV-2 spike protein (S protein) is inserted here.

CanSinoBIO has already used an adenovirus vector technology platform to develop a recombinant Ebola vaccine, as well as a tuberculosis booster vaccine and a shingles vaccine.

Acceleration of production potential

After comparing a variety of atomizing inhaler devices on the market, CanSinoBIO chose a vibrating mesh nebulizer from Galway-based company Aerogen for its vaccine which produces droplets two to five micrometers in diameter and has the less impact on the potency and structure of the vaccine.

Zhu’s team says the inhalable vaccine requires only one-fifth the dose of an intramuscular vaccine, which can help the vaccine maker retain more doses and increase production capacity.

CanSinoBIO’s vaccine can also be stored and transported in refrigerators between 2°C and 8°C, which is more favorable in countries with insufficient storage facilities and medical resources.

To establish a large-scale production process for the inhalable vaccine, Zhu says the challenge is to compare the different cell culture methods, with the team ultimately deciding that infusion culture was the best fit. Perfusion culture allows for greater automation with fewer manual operations, while ensuring production quality, stability and flexibility, allowing for increased production without a significant increase in manufacturing space.

“Another challenge we’ve had is getting regulators to accept a vaccination schedule for sequential inhaled vaccines,” Zhu says.

The company is also studying the possibility of using its vaccine as a heterologous booster dose.

CanSinoBIO aims to continue to develop COVID-19 Variants of Concern (COV) vaccines and other inhalation vaccines.

“The aerosolized version of our vaccine provides early evidence for stimulation of humoral, cellular and mucosal immunity,” says Zhu.

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