Why vaccines can provide better immunity than actual infections

Two recent studies have confirmed that people who were previously infected with SARS-CoV-2, the virus that causes COVID-19, may be re-infected with the virus. Interestingly, the results of the two were different. of Hong Kong people The second infection had no symptoms, Reno, Nevada, The second time I had a more serious illness. Therefore, it is unclear whether the immune response to SARS-CoV-2 prevents subsequent reinfection.

Does this mean vaccine Also fails to protect from Virus?? Certainly not. First, it is still unclear how common these reinfections are. More importantly, the diminished immune response to natural infections, as seen in patients in Nevada, does not mean that successful protective vaccines cannot be developed.

All infections first activate a non-specific innate immune response, white blood cells cell Causes inflammation. This will wipe out the virus. However, longer-term infections activate the adaptive immune system. Here, T cells and B cells recognize different structures (or antigens) derived from the virus. T cells can detect and kill infected cells, and B cells produce antibodies that neutralize the virus.

This adaptive immune response is delayed during primary infection, the first infection with a particular virus. It takes several days for immune cells that recognize a particular pathogen to activate and spread to control the infection.

Some of these T cells and B cells Memory cell, It lasts long after the infection is resolved. It is these memory cells that are essential for long-term protection. Subsequent infections with the same virus rapidly activate memory cells, eliciting a strong and specific response to block the infection.

Vaccines mimic this primary infection, provide antigens that stimulate the adaptive immune system, and produce memory cells that can be rapidly activated during the actual infection. However, the vaccine antigens are derived from weakened or non-infectious substances of the virus, so there is little risk of severe infection.

Better immune response

Vaccines have other advantages over natural infections. First, it can be designed to focus the immune system on specific antigens that elicit a better response.

For example Human papillomavirus (HPV) vaccine It provokes a stronger immune response than infection by the virus itself. One reason for this is that the vaccine contains high levels of virally infectious proteins. This triggers a strong neutralization of the antibody, and the vaccine is very effective in preventing infection.

of Innate immunity Resistance to HPV is particularly weak because the virus uses a variety of tactics to evade the host’s immune system. Many viruses, including HPV, contain proteins that block the immune response or simply low proteins to avoid detection. Indeed, vaccines that provide antigens accessible in the absence of these other proteins may allow natural infections to control their response in ways that they do not.

You can also adjust the immunogenicity of the vaccine, that is, how effective the vaccine is in producing an immune response. Agents called adjuvants can usually initiate an immune response and increase the immunogenicity of the vaccine.

In addition to this, doses and routes of administration can be controlled to stimulate the right immune response in the right place. Traditionally, vaccines are given by injection into the muscle, even in the case of respiratory viruses such as measles. In this case, the vaccine produces a strong response that allows antibodies and immune cells to reach the mucosal surface of the nose.

However Successful oral polio vaccine Reducing polio infection and transmission is due to a local immune response in the intestine where poliovirus replicates. Similarly, when the coronavirus vaccine is given directly to the nose, Mucous membrane Immunity Located in the nose and lungs, it protects the area of ​​invasion.

Understanding innate immunity is the key

A good vaccine that improves innate immunity must first understand innate immunity Immune response To the virus. So far, neutralizing antibodies against SARS-CoV-2 was detected Up to 4 months later infection..

Previous the study Antibodies to the associated coronavirus suggest that it typically lasts for several years. However, lower antibody levels do not always lead to lower immune responses. And more promising, recent Investigation It has been found that memory T cells provoke a response to the coronavirus, causing SARS about 20 years after people are infected.

approximate 320 vaccine Developed for COVID-19, which supports strong T cells response It may be the key to long-lasting immunity.

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