First-line immune defenses against COVID-19 are short-lived and may account for reinfection

A new study shows that antibodies produced in the nose decline after nine months of infection with COVID-19, while antibodies found in the blood persist for at least a year.

Antibodies in nasal secretions (called immunoglobulin A, or IgA) provide the first line of defense against COVID-19 by blocking the SARS-CoV-2 virus when it first invades enter the respiratory tract. This antibody very effective in preventing viruses from entering cells and causing infection.

However, the investigators found that the antibodies in the nose were present only in recently infected individuals and were particularly short-lived for the omicron variant compared with earlier variants.

These new findings—published in eBioMedicine—could explain why people who have recovered from COVID are at increased risk of reinfection, especially with omicron and its sub-variants.

Research also shows that vaccination is very effective in creating and strengthening antibodies in the body. bloodprevent serious diseasebut had little effect on nasal IgA levels.

First author of the study, Dr Felicity Liew, from the National Heart and Lung Institute at Imperial College London, said: “Before our study, it was not clear that these important nasal antibodies existed. Our study found sustained immune responses after infection and vaccination, but the important antibodies in this nose are shorter-lived than those in the blood. Antibodies in the blood help protect against disease, but antibodies in the nose can completely prevent infection, which could be an important factor behind reinfection with the SARS-CoV-2 virus. and its new variants.”

The researchers note that studies directly studying these nasal antibodies and reinfection are needed to confirm their results.

The study was led by teams from Imperial College London and the University of Liverpool. It studied nearly 450 people who were hospitalized with COVID-19 between February 2020 and March 2021, before the omicron variant and before the omicron variant. vaccine deployment.

The study also found that although current vaccines are effective at boosting blood antibodies that can prevent serious illness and death, they do not significantly increase IgA antibodies in the blood. nose.

Researchers call for next generation of vaccines to include nasal sprays or inhaled vaccines that target these antibodies more effectively. They say vaccines that boost these antibodies could potentially reduce infection more effectively and prevent transmission.

Study co-lead author Professor Peter Openshaw, from the National Heart and Lung Institute at Imperial College London, said: “Our results highlight a possible increased need for a nasal spray vaccine. strengthen these local antibodies in the nose and lungs.Such vaccines can prevent people from becoming infected with the SARS-CoV-2 virus and reduce the transmission of the virus between people. could help us better control the pandemic and prevent new variants from emerging.”

He continued: “Our current vaccines are designed to reduce severe illness and death and are remarkably effective in this goal. For now, it is essential to develop a spray vaccine. the nose can better protect against infection.It’s great that current vaccines mean that fewer and fewer people become seriously ill, but it would be better if we could prevent them from becoming infected and transmit the virus.”

The study analyzed the participants’ antibodies to understand how long the antibodies in the nose lasted compared to those found in the blood. They also studied the effect of the next COVID-19 vaccine on antibodies in the nose and blood.

Samples were taken when people were hospitalized and at 6 months and 1 year. Since most people were vaccinated during the study, many samples were also taken before and after vaccination.

They measured the effectiveness of the antibodies that neutralized the original SARS-CoV-2 virus as well as the delta and omicron variants to see how long the antibodies were effective after infection or injection. Vaccine.

The study included 446 people hospitalized during the early stages of the pandemic, of whom 141 provided samples at the start of the study and 6 and 12 months later. For participants who took only one sample during the 12-month study period, the researchers used the model to estimate how the average antibody responses changed over time.

Of those who confirmed they had been vaccinated (323), 95% (307) had been vaccinated for the first time during the study follow-up period. This results in an increase in all antibodies in the nose and in the blood, but the change in first-line defensive nasal antibodies (IgA) is small and temporary. The researchers found that the gender, severity of the disease and the age of the participants had no effect on how long their nasal immunity lasted, but note that their study only in people with severe illness requiring hospitalization.

They also found that the antibodies in the participants’ blood continued to bind to the original SARS-CoV-2 virus as well as the delta and omicron variants one year after infection, but found that booster vaccine to maintain this immunity.

The study’s senior co-author, Dr Lance Turtle, Senior Clinical Lecturer at the University of Liverpool and Consultant Infectious Diseases at Liverpool University Hospital, said: “Our study showed that this first-line defensive immunity is separate from other immune responses, and although it is increased by vaccination and infection, it only lasted for about nine months. However, booster vaccines can slightly increase this rate and on the other hand have a significant impact on other areas of immunity, very effective protection against severe illness and death, so it is still very important. important.”

The researchers note that their study did not screen participants for reinfection, but this is unlikely because the study took place during a period of national restrictions and closures when COVID incidence rates -19 is low and people are not socializing with each other. In a preliminary analysis, they found only two reinfections in their study, suggesting that the general trends found to be correct.