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Explainer: When will nasal vaccines for Covid-19 be ready, and does it matter to Singapore?

SINGAPORE — Two years since the outbreak of the coronavirus causing Covid-19, more than 100 vaccine candidates are still being tested, including nasal vaccines that are administered through the nose.

Explainer: When will nasal vaccines for Covid-19 be ready, and does it matter to Singapore?
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  • Covid-19 vaccines that are administered through the nose instead of by injections are undergoing clinical trials
  • WHO has expressed optimism for such vaccines, highlighting benefits such as easier administration
  • Singapore experts talked about the potential of nasal vaccines to halt the virus before it enters the body, effectively stopping transmission
  • However, they emphasised that conclusions cannot be drawn before clinical results are out
  • The impact of nasal vaccines on Singapore may not be great, some said

SINGAPORE — Two years since the outbreak of the coronavirus causing Covid-19, more than 100 vaccine candidates are still being tested, including nasal vaccines that are administered through the nose.

Scientists in Japan and India are among those recently reported to be conducting clinical trials for these vaccines, known in the medical world as intranasal vaccines.

They would be typically delivered via nasal spray and thus have the decided advantage of not requiring intravenous injections.

Esco Aster, a homegrown biotechnology company, was last year reported to be working with an American firm to develop a vaccine delivered as a nasal spray. 

Some scientists around the world are expressing optimism about the prospect of this needle-free form of inoculation against Covid-19.

They said that such vaccines may be easier to distribute and are potentially very effective at inducing an antibody reaction in the nasal cavity when the virus first enters a body.

Some experts here told TODAY that by the time such vaccines see the light of day in the market, their impact may be limited, particularly for a highly vaccinated population such as Singapore's. 

However, they highlighted the potential advantages of intranasal sprays and expect that the benefits may be more evident in vaccination programmes down the track.

This means not even mild or asymptomatic disease, and therefore, no transmission.
Professor Dale Fisher, infectious diseases expert, on the potential benefits of nasal Covid-19 vaccines

HOW THEY WORK AND THEIR EFFICACY

Intranasal vaccines work by inducing an antibody reaction in the mucous membrane of the nasal cavity, the entry point for the Sars-Cov-2 virus that causes Covid-19.

Professor Dale Fisher, a senior consultant in infectious disease at the National University Hospital, explained: “This is where the body will mount a different antibody response called IgA as opposed to the existing vaccines, which work mostly in the blood with IgM and IgG.”

As the virus is prevented from entering the body, this would theoretically mean that such vaccines would prevent any infection at all.

“This means not even mild or asymptomatic disease, and therefore, no transmission,” Prof Fisher said.

Dr Leong Hoe Nam from Rophi Clinic, which specialises in infectious diseases and vaccinations, said: “Nasal mucosa vaccinations were much coveted for respiratory tract viruses for that theoretical advantage.”

However, these experts emphasised that the real-life efficacy of these vaccines will not be clear until the results of clinical trials are available.

Associate Professor Hsu Li Yang, vice-dean of global health at NUS Saw Swee Hock School of Public Health, cited the example of intranasal vaccines that have been available for influenza for years. The intranasal vaccine for flu is a live vaccine.

“Compared against intramuscular flu shots, they are not definitively better at preventing flu except perhaps in children,” he told TODAY.

“However, these are different diseases and vaccines, so they are not directly comparable.”

SIMPLER, FASTER ADMINISTRATION

Administering vaccines through the nasal cavity would be a simpler process compared to giving jabs, the experts here said.

This is in line with the views expressed by the chief scientist of the World Health Organization (WHO) in November last year. 

Dr Soumya Swaminathan said then that she was looking forward to the "second generation" of Covid-19 vaccines, which could include nasal sprays and oral versions, because they would be easier to deliver than injections.

They could even be self-administered, she added.

Such an advantage would be more felt in poorer countries, based on a report published in medical journal The Lancet in late January.

The report also stated: “Another advantage of intranasal vaccines is that they do not require a sterile environment for administration, which benefits vaccination programmes in countries with fewer resources.”

It added that this would also pave the way for quicker roll-out of immunisation programme.

HOW FAR AWAY ARE WE?

Regardless, it may be a long time before such advantages and benefits can be seen in the real world.

Even with the accelerated process of approvals, I believe we will only see (nasal Covid-19 vaccines) being commercially available at the end of 2022 or start of 2023.
Associate Professor Hsu Li Yang, vice-dean of global health, NUS Saw Swee Hock School of Public Health

The Lancet report last month stated that 12 intranasal vaccines were undergoing various stages of clinical trials as of late January. 

The report listed a nasal spray vaccine developed by University of Hong Kong, Xiamen University and Beijing Wantai Biological Pharmacy as undergoing third-phase clinical trials, as is one developed by Iran’s Razi Vaccine and Serum Research Institute.

In late January, India’s Bharat Biotech also received the green light by the authorities there to carry out late-stage trials of its nasal Covid-19 vaccine to be used as a booster shot.

Japanese pharmaceutical company Shionogi is also expected to start clinical trials for a Covid-19 nasal spray vaccine this year, a report by the country's Nikkei news outlet said.

Singapore's national daily The Straits Times in March last year reported that Esco Aster was working with American company Vivaldi Biosciences to develop a vaccine in the form of a nasal spray. TODAY has contacted Esco Aster to seek comment on its progress.

The experts who spoke to TODAY agreed that these intranasal vaccines are not likely to be available in the market anytime soon.

Dr Paul Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection, said that the timeline and process that these vaccines have to go through to get approved would be similar to the existing Covid-19 vaccine jabs.

For example, the Pfizer-BioNTech vaccine against Covid-19 got WHO’s approval for emergency use in December 2020, about seven months after starting clinical trials. 

Assoc Prof Hsu from NUS Saw Swee Hock School of Public Health said: “Even with the accelerated process of approvals, I believe we will only see those being commercially available at the end of 2022 or start of 2023.”

Dr Leong of Rophi Clinic succinctly expressed his pessimism with regard to the timeline: “Don't hold your breath — you will turn blue.”

IMPACT ON SINGAPORE

The experts expressed mixed views on the impact of an intranasal Covid-19 vaccine on Singapore if and when it should become available.

Owing to the lengthy timeline before such vaccines reach the market, Assoc Prof Hsu said that such intranasal vaccines would just be an alternative choice rather than a replacement for existing jabs.

This is “unless the clinical trial and real-world outcomes are truly superior to the existing vaccines”, he said.

The trajectory of the nasal flu vaccines has been a cautionary tale for manufacturers, with only one that is commercially widely available. I hope I am wrong as many people I know don’t like needles!
Dr Paul Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection

Dr Tambyah echoed his sentiments, saying that Singapore's population would have achieved hybrid immunity — protection rendered by vaccination and natural infection — by the time the intranasal vaccines conclude late-stage trials.

“As such, the market for another type of vaccine is likely to be small and the chances of it becoming widely marketed in high income countries are low.

“The trajectory of the nasal flu vaccines has been a cautionary tale for manufacturers, with only one that is commercially widely available. I hope I am wrong as many people I know don’t like needles!” he added.

However, Dr Leong and Prof Fisher were more optimistic.

Dr Leong foresees Covid-19 vaccines as being part of the childhood vaccination programme. Thus, a nasal vaccine would be “much better tolerated” than injections and would benefit future generations of the population here, he said.

Prof Fisher emphasised the hypothetical ability of nasal vaccines in stopping Covid-19 transmission.

“There are many advantages in preventing transmission everywhere. The threat of new variants would also decline,” he said.

Related topics

Covid-19 coronavirus vaccination nasal spray coronavirus vaccine nasal vaccine

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