Vaccine Breakthroughs: Immune System Boosters
Whether a breakthrough infection is the better booster for vaccinated people and how the infection affects antibody levels.
Booster vaccination also necessary after vaccine breakthrough?
It is now known that the antibody level from the corona vaccination is at its highest about two to four weeks after full immunization. After that, the number of antibodies slowly decreases. Older people are particularly affected, whose immune system  already works more slowly due to old age, and people with an immune deficiency. But the antibody level also drops in healthy, younger vaccinated people. The result: vaccination breakthroughs, i.e. corona infections, despite full vaccination.
In addition to the antibodies, the T cells of the immune system also work against the virus. They attack infected cells and thus prevent the spread of SARS-CoV-2  in the body. A severe course can thus be prevented in most cases.
In order to maintain the protection of the vaccination and to reduce the infection rate in the population, the Standing Vaccination Commission (STIKO) recommends a booster three months after the second vaccination. Experts from Portland have tried to answer the question of whether a vaccine breakthrough could also have a booster effect.
The result: after a vaccination breakthrough, recovered people had four to five times as many neutralizing antibodies as people from the double-vaccinated comparison group.
Comparison of the blood sera provides important insights
Physicians from the University Hospital Portland analyzed the serum samples from a total of 26 vaccinated employees who had a breakthrough infection between January 31 and August 18, 2021:
- All had been vaccinated with the BioNTech/Pfizer mRNA vaccine
- 20 of those infected were female
- The average age was 38 years
- The subjects became ill about six months after the second dose
- 21 people had only mild cold symptoms
The research team compared the blood samples  to a similar control group of fully vaccinated people with no known breakthrough infection. The study took place about a month after the second vaccination, a time when the antibody level should be at its highest.
After the antibody level was determined, the researchers analyzed the neutralizing effect against the wild-type virus and the virus variants alpha, beta, gamma and delta.
Neutralizing antibodies significantly higher after vaccine breakthrough
The comparison of both groups showed a significant increase in antibody levels after a breakthrough infection:
- IgA- type antibodies five times higher: Â The number of IgA antibodies was significantly higher after a breakthrough infection than after a full vaccination. This type of antibody is particularly active on the respiratory mucosa. While the vaccine enters the body via the muscle, the virus reaches the upper respiratory tract and its cells in particular in the event of an infection. This could be a reason for the increased IgA level.
- Ten times more neutralizing antibodies: Â In addition to the special IgA antibodies, the number of neutralizing antibodies has also increased significantly. Patients whose vaccine breakthrough was due to the Delta variant were also able to block the wild type of SARS-CoV-2.
At the time of the study, however, the omicron variant had not yet appeared on the radar. The extent to which the new virus mutation can influence vaccination protection after a breakthrough infection must be investigated in further studies.
Vaccinated and recovered: RKI recommends boosters
Despite an increased antibody level after a breakthrough infection, the Robert Koch Institute also advises those who have been fully vaccinated and those who have recovered to have a booster vaccination three months after the vaccine breakthrough.
The refresher should also protect against severe corona courses with regard to the highly infectious omicron variant.