In late 2021, the pandemic entered a new phase. Many people weren’t sure if they were at high risk of contracting it despite being vaccinated and having suffered COVID-19 infection in the past.
The vast majority of the population has been immunized against COVID-19 or has recovered from infection in the past few years. Many people are now asking: What time can vaccinations, active infections, or both, trigger the immune system?
It is difficult to answer this question as the virus remains relatively new. There are always new variants of the virus. This makes it difficult to answer.
We are immunologists that study infectious and inflammatory diseases, including COVID-19. Our goal is to understand how protective immunity works.
Antibodies, Killer T Cells: What are their roles?
After being infected by COVID-19, or vaccinated, your body will produce two types of immune defenses. B cells produce antibodies.
Antibodies (Y-shaped proteins) are the first line of defense against infection. Once the virus is in a cell, it can spread to other cells.
This is when your immune system activates another kind of immune cell, called the killer T cell. These cells are your second line of defense.
Killer cells cannot detect viruses in cells. They can destroy viruses before they spread.
Incorrectly, the public believed that antibodies provided most of the protective immunity during the COVID-19 epidemic. They did not recognize the critical role played by killer cells.
Protective immunity for long-term is dependent upon memory
The true veterans of the immune system are those who have a lot of experience and can provide long-lasting immunity and protection against infections.
The virus or its spike protein has been cleared. These cells respond quickly by recognizing the virus and releasing antibodies.
Multiple doses of COVID vaccines are better than one. An identical increase in the number of memory-killing T cell cells can help to prevent serious illness and hospitalization.
Memory cells can be kept in place for long periods of time by the immune system.
But, memory cells can be very specific. If new strains or viruses emerge, memory cells may not work as well.
It begs the question, “When and for how long?”
Long-term resistance to COVID-19
Antibodies begin to mobilize after infection with COVID-19 or after vaccination. The Centers for Disease Control and Prevention believes that people will experience a “waning immune” around the time they turn 2021.
Immunity is complex and nuanced. However, antibodies are only one aspect of it. Memory killer T cells can be detected up to 2 years after COVID-19 infection.
It is well-known that vaccines can cause immune memory similar to natural infection. A new study, however, which has not been peer-reviewed, found that vaccines increase B cell diversity. This increases protection against variants like omicron.
But, the detection and confirmation of an immune response do not guarantee protection against COVID-19.
Due to the research and time required, it is difficult to determine if the protection provided with killer cells and antibodies was correlated with the amount of COVID-19.
It’s now apparent that the virus may have an immune response, but it is not sufficient to prevent reinfection.
Immunity to Infection from Vaccination
Recent U.K. Health Security Agency studies showed that two doses can protect against infection for as long as six weeks. A second study revealed that mRNA vaccines had a protective effect of two months. Their effectiveness fell to seven months because of the emergence and decrease in infection.
Conflicting reports exist about whether active infection triggers protective immunity. This could be due to the variety of virus strains that were discovered during the study.
COVID-19 is believed to provide protection similar to that offered by vaccines. This was however not peer-reviewed.
Hybrid immunity
Researchers discovered that hybrid immunity (coviD-19 plus vaccination) can provide very strong protection against infection. This protection continues to be active for more than a year after infection with COVID-19.
A unique type of hybrid immunity, Hybrid immune triggers an antibody response that lasts for a long time.
Researchers are trying to find vaccines that can trigger the same long-term immune response as other people to reinfect them. This is a growing fact.
