Many people who have had Covid they reinfect, some much sooner than appears to be normal. The reason may lie, according to a new study published in “eBioMedicine”, in that the antibodies produced in the nose decrease nine months after infection by Covid-19, while those found in the blood last at least a year. That is, the immunity generated is not very long-term.
The trial also found that while current vaccines are effective at raising blood antibodies that can prevent serious illness and death, do not significantly increase nasal IgA antibodies.
Antibodies present in nasal fluid (known as immunoglobulin A or IgA) provide a first-line defense against Covid-19 by blocking the SARS-CoV-2 virus when it first enters the airways. These antibodies are very effective in preventing the virus from entering cells and causing infection.
But, as this work explains, the nasal antibodies were only present in the newly infected and were especially short-lived against the Omicron variant, compared to previous variants.
These new findings may explain why people who have recovered from Covid are at risk of reinfection, and especially with Omicron and its subvariants.
The study also revealed that vaccination is very effective at creating and increasing antibodies in the blood, which prevent severe disease, but has little effect on levels of IgA in the nose.
“Prior to our work, it was not clear how long these important nasal antibodies lasted. Our study revealed long-lasting immune responses after infection and vaccination, but these key nasal antibodies were shorter-lived than those in blood. While blood antibodies help protect against disease, nasal antibodies can prevent infection completelyeither. This could be an important factor behind repeated infections with the SARS-CoV-2 virus and its new variants,” said study first author Felicity Liew, from the National Heart and Lung Institute at Imperial College London.
The research was led by teams from Imperial College London and the University of Liverpool (UK). He studied almost 450 people who had been hospitalized with Covid-19 between February 2020 and March 2021, before the appearance of the Omicron variant and before the rollout of the vaccine.
Researchers call for the next generation of vaccines to include nasal sprays or inhaled vaccines that target these antibodies more effectively. They claim that vaccines capable of boosting these antibodies could more effectively reduce infections and prevent transmission.
“Our results highlight the need for nasal spray vaccines that can boost these local antibodies in the nose and lungs. These vaccines could prevent people from becoming infected with the SARS-CoV-2 virus and reduce transmission of the virus from person to person. This could help us better control the pandemic and prevent the appearance of new variantssays the study’s co-senior author, Professor Peter Openshaw.
Adds Openshaw, “Our current vaccines are designed to reduce severe disease and death, and they are spectacularly effective at this goal. It is now essential to also develop vaccines in aerosol nasal They may provide better protection against infection. It’s brilliant that current vaccines allow fewer people to get seriously ill, but it would be even better if we could prevent them from getting infected and transmitting the virus.”
Current vaccines are designed to reduce severe disease and death, and are spectacularly effective at this goal.
The study tested the participants’ antibodies to see how long the nasal antibodies lasted, compared to those found in the blood. They also studied the effect of subsequent Covid-19 vaccines on antibodies from the nose and blood.
Samples were taken when people were hospitalized and six months and one year later. Since most people were vaccinated during the study, many samples were also taken before and after vaccination.
The efficacy of antibodies to neutralize original SARS-CoV-2 virus and variants was measured Delta and Omicron, to see how long the antibodies were effective after infection or vaccination.
Of those who confirmed whether they had been vaccinated (323 people), 95% (307 people) received their first vaccination during the follow-up period of the study. This caused increases in all nasal and blood antibodies, but the change in nasal first-line defense (IgA) antibodies was small and temporary. The researchers found that the participants’ gender, disease severity and age had no influence on the duration of their nasal immunity, but caution that their study was only done in people with severe illness that required hospitalization.
The study suggests that this first-line immunity is independent of other immune responses and, while increased with vaccination and infection, only lasts for about nine months.
They also found that the participants’ blood antibodies continued to bind to the parent SARS-CoV-2 virus and the Delta and Omicron variants one year after infection, but concluded that booster vaccinations are necessary to maintain this immunity.
“Our study suggests that this first-line defense immunity is independent of other immune responses and, although it increases with vaccination and infection, it only lasts for about nine months. Nevertheless, lBooster shots can increase it slightly and otherwise have a significant impact on other areas of immunityprotecting against severe disease and death very effectively, so they remain very important,” said study co-author Lance Turtle, Senior Clinical Lecturer at the University of Liverpool and Infectious Diseases Specialist at Liverpool University Hospitals. .
The researchers acknowledge that their study did not test participants for reinfections, but that this was unlikely to occur as the study took place during periods of national restrictions and lockdowns, when the incidence of Covid-19 was low and people did not mix. In a preliminary analysis, they found only two cases of reinfection in their study, suggesting that the general trends observed are correct.