[OPINION] Could Inhaled Vaccination be the Endgame for COVID-19 Elimination? 

(Photo: Mockup Graphics/Unsplash)


By Dr Thaigarajan Parumasivam 

Inhaled or aerosol vaccine delivery which mimics the natural route of COVID-19 infection, has attracted significant attention for the management of the disease and several clinical trials have been registered. 

Recently, CanSino Biologics (China) published the first randomised, single-centre, open-label, phase 1 trial of inhaled vaccination of adenovirus type-5 vector-based COVID-19 vaccine (Ad5-nCoV). It is a collaborative study with the Beijing Institute of Biotechnology, Academy of Military Medical Sciences led by Prof Lihua Hou. The trial was conducted in Zhongnan Hospital, Wuhan, China. This vaccine is already approved for use in a single-dose, injectable form in China, Pakistan and Mexico. 

The aerosolised Ad5-nCoV was found to be well tolerated by the participants, and two doses of the vaccine triggered immunity similar to one dose intramuscular injection. Additionally, the booster dose via aerosolisation at 28 days post-intramuscular injection elicited robust antibody responses. Currently, the researchers proceeding with the aerosolised vaccine to phase 2 and phase 3 clinical trials. 

The advent of inhalation as a potential route for vaccination of COVID-19 has a number of plusses compared to conventional administration. Nonetheless, several challenges need to be addressed. Let’s see them. 

How does the inhaled vaccine work?

Nebuliser is a popular device for pulmonary vaccination. The nebuliser generates aerosol medication from liquid or suspension vaccine formulations in the form of mist using compressed gas or ultrasonic waves. When someone inhaled this mist, the antigenic particles will be deposited in his/her respiratory system.  

The respiratory system comprises of a mucosal network of immune cells for immunity. They are strictly regulated to confer protection against detrimental airborne pathogens. Because of this extensive interface of interaction between immune cells and airborne antigenic particles, the aerosol deposition of antigens into the lungs will readily trigger local immunity. 

What are the advantages of inhaled vaccination?

Inhale vaccination is noninvasive that is needle-free, and negates the requirement for the disinfection of injection sites and disposal of the needles. This can save the cost of the disinfectant, sterile needles and syringe as well as the cost of the waste disposal. Though no evidence of SARS-CoV-2 transmission through blood, the inhale medication may reduce the risk of bloodborne diseases (i.e. HIV and hepatitis B and C) with consequent mortality due to unsterilised needles. 

The need for a high dose could be reduced via inhale route of administration. Aerosol vaccination may best mimic the immune response in the pulmonary region followed by systemic immunity. Hence, inhalation of vaccine particles simulates the natural route of infection by SARS-CoV-2 and could be more efficient at stimulating immune responses than the common route of intramuscular injections.

What are the challenges of inhaled vaccination?

If the vaccines manufactured into inhalable forms are expensive, this will reduce the global accessibility of the therapy, especially to the low-income countries, including Malaysia. If this hurdle can be mitigated satisfactorily, inhaled therapy has the potential to significantly contribute to the global elimination of COVID-19. It is undeniable that cheaper manufacturing and packaging will be advantageous. 

Well trained staff are also crucial in the health care set-up to instruct on the proper use of inhaler devices to harvest the optimal benefits of inhaled vaccination as well as to prevent hospital-acquired infections among the staff in the hospital. This may incur additional costs to the treatment. This is critical due to severe and mounting disruption to the global supply of personal protective equipment (PPE) in healthcare settings. 

In conclusion, if these hurdles can be mitigated, the inhaled vaccination has the potential to contribute to the global elimination of COVID-19. Certainly, a cost-benefit analysis is crucial to justify the global implementation of inhaled vaccination for COVID-19.  

* This is the personal opinion of the writer or publication and does not necessarily represent the views of Science Media Centre Malaysia

**All previous posts about COVID-19 here: https://sciencemediacentremalaysia.com/tag/covid-19/

Dr Thaigarajan Parumasivam is a senior lecturer at the School of Pharmaceutical Sciences, Universiti Sains Malaysia. He is an affiliate of the Young Scientist Network – Academy of Sciences Malaysia (YSN-ASM) and an honorary secretary of the Malaysian Society of Pharmaceutical Technology (MSPT).

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