The next generation of COVID vaccines should include nasal sprays because other vaccines have limited impact on protective levels in the nose, British researchers have suggested.
Antibodies produced in the nose decline nine months after infection while those in the blood last at least a year, researchers reported.
A UK study has found that immunoglobulin A (IgA) in the nose blocks SARS-CoV-2 virus when it first enters the respiratory tract and these are effective at preventing the virus from entering cells and causing infection.
The research, led by teams from Imperial College London and the University of Liverpool, studied 446 people who had been hospitalised with COVID-19 between February 2020 and March 2021.
They found nasal antibodies were only present in individuals who had been recently infected and were particularly short-lived against the Omicron variant.
Writing in eBioMedicine, they say it may explain why people who have had COVID-19 are at risk of reinfection, especially with Omicron and its subvariants.
Nine months
While vaccination creates and boosts antibodies in the blood, which prevent severe disease, they had very little effect on nasal IgA levels, which has resulted in the researchers to call for the next generation of vaccines to include nasal spray or inhaled vaccines that target these antibodies more effectively.
First study author Dr Felicity Liew, from the National Heart and Lung Institute at Imperial College London, said: “Before our study, it was unclear how long these important nasal antibodies lasted. Our study found durable immune responses after infection and vaccination, but these key nasal antibodies were shorter-lived than those in the blood.
“While blood antibodies help to protect against disease, nasal antibodies can prevent infection altogether. This might be an important factor behind repeat infections with the SARS-CoV-2 virus and its new variants.”
Co-senior author Professor Peter Openshaw, from the National Heart and Lung Institute at Imperial College London, added: “Our results highlight a need for nasal spray vaccines that can boost these local antibodies in the nose and lungs.
“Such vaccines might be able to prevent people from getting infected with the SARS-CoV-2 virus and reduce transmission of the virus between people. This could help us to better control the pandemic and stop new variants emerging.”
The study included 446 people admitted to hospital in the early phase of the pandemic, including 141 who provided samples at the start of the study and six and 12 months later.
Researchers used modelling to estimate how the average antibody responses changed over time among those who only had one sample taken during the 12-month period of study.
Of the 323 who confirmed they had been vaccinated, 307 (95%) received their first vaccination during the study follow-up period, which resulted in increases in all nasal and blood antibodies. However, the change in the first-line defence nasal antibodies (IgA) was small and temporary.
They also found the participants’ blood antibody continued to bind the original SARS-CoV-2 virus, and the Delta and Omicron variants, a year after infection. Booster vaccines are needed to maintain this immunity.
Co-senior study author Dr Lance Turtle, senior clinical lecturer at the University of Liverpool and consultant in infectious diseases at Liverpool University Hospitals, said: “Our study suggests that this first-line defence immunity is separate from other immune responses, and although it is increased by vaccination and infection, it only lasts for about nine months.
“Nonetheless, booster vaccines can increase it slightly and otherwise have a significant impact on other areas of immunity, protecting against severe disease and death very effectively, so remain very important.”
The team says further research into nasal antibodies and reinfections are needed to confirm their results.
eBioMedicine 19 December 2022
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