A new study from King’s College London found a delta breakthrough infection generates a potent and broad neutralizing antibody response in double vaccinated individuals.
The study is published in mBio and was conducted by Katie Doores et al.
In the study, the team collected sera from individuals who tested positive for COVID-19 and had received 2 doses of either the Pfizer or AstraZeneca vaccines.
They measured how much antibody the person produced and whether the antibodies were able to prevent infection of cells by different SARS-CoV-2 variants of concern.
The researchers found that in vaccinated individuals, there was a rapid and robust IgG recall response following breakthrough infection.
This antibody response had broad neutralizing activity against current variants of concern, including omicron.
The neutralization potency was 4.5-fold reduced against omicron compared to delta, whereas it was 28.9-fold reduced for people who were unvaccinated.
The finding suggests that a breakthrough infection effectively boosts the vaccine response, which could provide broad protection against current variants of concern
Recent studies show a third vaccine dose dramatically increases the neutralizing antibody response, particularly against omicron.
For example, a study from Kaiser Permanente found that three doses of the Moderna COVID-19 vaccine were highly effective against hospitalization caused by the Omicron or Delta variant.
That study included 26,683 patients who tested positive for COVID-19, 16% of whom had Delta infections and 84% of whom had Omicron infections, and more than 67,000 individuals who tested negative as a comparison group.
The team found two doses of the Moderna COVID-19 vaccine were 44% effective against Omicron infection within 3 months after vaccination, and effectiveness quickly declined thereafter.
Three doses of the Moderna COVID-19 vaccine within 2 months of vaccination were 94% effective against Delta infection and 72% effective against Omicron infection.
For people who had compromised immune systems, 3-dose effectiveness against Omicron infection was lower at 29%.
The 3-dose effectiveness against hospitalization with Delta or with Omicron was above 99%.
The results suggest that third doses may be needed sooner than 6 months after the second dose of the Moderna COVID-19 vaccine to protect against Omicron infection.
Related: scientists find drug duo that may cure COVID-19 together.
Another study from the Technical University of Munich found the immune system develops a high-quality antibody response after three encounters with the coronavirus spike protein.
These antibodies are also capable of neutralizing omicron efficiently.
This applies to people who are triple-vaccinated, to those having recovered and then received two vaccinations, and to double-vaccinated individuals who have experienced a breakthrough infection.
Since the beginning of the COVID-19 pandemic, SARS-CoV-2 has continued to evolve, with new variants of concern (VoCs) spreading rapidly.
Highly contagious and partially capable of evading the immune response, omicron has become the dominant variant in most countries.
In that study, the team found a total of three exposures to the viral spike protein leads to the production of virus-neutralizing antibodies not only in high quantity but also high quality.
These high-quality antibodies bind to the viral spike protein more vigorously and are also capable of effectively fighting the omicron variant.
This applies to triple-vaccinated people, to people who have recovered from COVID-19 and then had two vaccinations, and to double-vaccinated people who then had a breakthrough infection.
the researchers identified individuals who had contracted SARS-CoV-2 during the first wave of the pandemic in spring 2020, and compared them to the second group of people who had not been infected.
Subsequently, both groups were offered vaccination with the mRNA-based COVID-19 vaccine from BioNTech/Pfizer and were monitored for almost two years.
The cohort comprised 98 recovered persons and 73 persons without prior infection.
The team found omicron exhibited the most pronounced evasion from neutralizing antibodies compared to all other viral variants tested.
For omicron, people need considerably more and better antibodies to prevent infection.
The researchers developed a new virus neutralization test, which allowed them to analyze antibodies in many serum samples and different variants of the virus at high throughput rates.
They showed that three separate exposures to the spike protein can build up high-level neutralizing activity against all viral variants, including omicron.
The new study suggests a delta breakthrough infection can also act as an effective booster.
This study provides insights into population immunity in double COVID-19 vaccinated individuals where SARS-CoV-2 transmission levels remain high.
If you care about COVID, please read studies about 16 drugs that could treat COVID-19, and why smokers have a lower risk of COVID-19.
For more information about COVID, please see recent studies that Moderna COVID vaccine is more effective against Delta, and results showing that vitamin D can be cheap treatments for COVID-19.
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