COVID-19 Nasal Spray Vaccine : The Prevention Effect is Better than the Intramuscular Vaccine?

The new coronavirus infection usually starts in the nasal cavity or pharynx, and the infection has taken root in the nasal cavity or pharynx before the systemic immunity begins. Therefore, a nasal spray vaccine that can produce both systemic immunity and local immunity has better preventive effects.

The main goal of the COVID-19 vaccine is to protect vaccinated persons from serious illness and death from infection with the new coronavirus. But the more important goal is to prevent the spread of disease. Although it is still unclear, most vaccine candidates under development can do this. Some scientists believe that this problem can be solved by vaccination through nasal spray.


Dr. Frances Lund, Director of the Department of Microbiology, University of Alabama at Birmingham School of Medicine (Source : University of Alabama at Birmingham official website)

Dr. Frances Lund, Charles H. McCauley Chair Professor and Chair of the Department of Microbiology at the University of Alabama at Birmingham School of Medicine, said that most vaccines, including all vaccines currently undergoing clinical trials, are administered intramuscularly. The intramuscular injection site is usually the deltoid muscle of the upper arm. Vaccination by intramuscular injection often produces a strong immune response, so most vaccine development agencies focus on intramuscular vaccines. Although intramuscular vaccination can produce a systemic immune response through the blood circulatory system, it cannot produce a local response.

For respiratory viruses such as the new coronavirus, the infection usually starts in the nasal cavity or pharynx, and the infection has taken root in the nasal cavity or pharynx before the systemic immunity begins. Intramuscular injection of the vaccine can protect the vaccinated from serious diseases, but the vaccinated may still carry the virus in the nasal cavity and spread to others. The nasal spray vaccine can provide another kind of immunity, which mainly exists in the cells of the nasal cavity and pharynx. If inoculated through the nasal cavity, in addition to gaining systemic immunity, it also increases a local immunity, which cannot be achieved with intramuscular vaccines. Systemic immunity can keep the vaccinated from getting sick, while local immunity means that it will be more difficult for the virus to start infection in the nasal cavity -- the virus in the 'infected bag' in the nasal cavity can easily spread to others through breathing or sneezing. Dr. Lund is working with Altimmune to develop such a vaccine.

If the new vaccine is completely effective and everyone is vaccinated, there is no need to worry about vaccinated people exhaling the virus to infect others, but this situation is difficult to achieve. Dr. Michael S. Diamond, Herbert S. Gasser Chair Professor of Medicine, Molecular Microbiology, Pathology and Immunology at the University of Washington, said that in addition to those who have not been vaccinated, there are some people who will not have enough vaccine responses, which means these The human body does not produce antibodies that protect the vaccinated person.

Everyone hopes to have a vaccine to prevent the spread of the virus, but it is not always technically feasible. The research team led by Dr. Diamond recently published a paper in 'Cell', showing that ChAd-SARS-CoV-2-S single-dose nasal spray vaccine can prevent SARS-CoV-2 infection in the upper and lower respiratory tracts of mice. The team plans to test the vaccine in non-human primates and humans to see if the vaccine is safe and effective in preventing infection.

Dr. Diamond said that although the current nasal spray vaccine is not common, there are vaccines for other diseases, such as the Flumist flu vaccine currently in use. Dr. Diamond hopes to use the existing nasal spray technology.

Similar to this strategy, on August 21, the 'Nature' sub-issue 'Nature Communications' published a report from Dr. Chen Ling from the State Key Laboratory of Respiratory Diseases, Dr. Yuan Zhiming from the Wuhan Institute of Virology, Chinese Academy of Sciences, and Guangzhou Enbao A signed paper by Dr. Guan Suhua of Biology, etc., reported an adenovirus vaccine (Ad5-S-nb2) that carries a gene sequence encoding a spike protein, and the sequence has been codon-optimized. Intramuscular injection of Ad5-S-nb2 in mice and rhesus monkeys can cause systemic spike protein-specific antibodies and cell-mediated immunity (CMI) responses. Intranasal vaccination can cause systemic and lung antibody responses, but the CMI response is weak. After 30 days of intramuscular injection or nasal spray inoculation of rhesus monkeys with Ad5-S-nb2 vaccine, it has a protective effect against SARS-CoV-2 challenge.

We expect that the nasal spray COVID-19 vaccine that can produce both systemic immunity and local immunity and better preventive effects will come out soon.