The vaccine protects the body better than natural immunity

Vaccines can create a "protective ring" more effectively than the natural immunity produced by the human body after an illness.

From two nCoV reinfection cases, in which one person showed no symptoms, the other got worse than the first infection, scientists have not been able to conclude the body's natural immunity to nCoV.

Any infection triggers a natural immune response, enough to completely kill the virus. However, in long-term infections, the adaptive immune system is activated. T cells detect and destroy virus-infected cells, and B cells create antibodies that neutralize the virus.

At the first infection, it takes a few days for the irritated immune system to recognize, destroy, and control the infection.

The vaccine was developed with the ability to mimic the first infection, provide antigens to support the immune system to adapt, create memory cells that can activate quickly if the virus first attacks the body. The antigens in the vaccine are derived from the non-infectious component of the virus, so the body is less likely to cause a serious infection.

In addition, vaccines can be formulated to help the immune system focus against specific antigens, creating a better response.

A volunteer gets a trial vaccination of Covid-19 in Hollywood, USA, April 2020. Photo: NY Times

The HPV vaccine against cervical cancer contains a higher concentration of viral envelope protein than a natural infection. This activates powerful neutralizing antibodies, giving you a high degree of infection prevention.

Meanwhile, natural immunity against HPV is particularly weak because the virus uses different "tactics", hiding the host's immune system. Many viruses, including cervical cancer, contain proteins that block the immune response or remain low in the host's body, avoiding detection. In fact, vaccines provide antibodies that allow them to control responses in a way that natural infections cannot.

The efficacy level in the immunization of the vaccine can also be adjusted. Pharmacological agents such as adjuvants often activate the immune response and can enhance the immunological effectiveness of vaccines. Humans can also control the dose of the vaccine and the route of the vaccine into the body to stimulate an immune response in place.

The traditional intramuscular vaccine reacts so strongly that antibodies and immune cells reach the mucosal surface in the nose. The oral polio vaccine produces a good immune response in the gut, where the polio virus replicates. Similarly, injecting nCoV vaccine directly into the nose can help strengthen immunity in the nasal mucosa and lungs, protecting the body from the nCoV where the virus easily penetrates.

Previous studies showed that antibodies against nCoV usually last for several years. However, decreased antibody levels do not always mean a poor immune response. More promising, a recent study found that T cells triggered anti-nCoV responses nearly 20 years after infection.

Of the nearly 320 Covid-19 vaccines being developed against nCoV, a vaccine containing strong T cells may be the key to long-term immunity in humans.