Previous Vaccine Infections: Why Everyone Should Get the COVID-19 Vaccine

Infections provide some immunity to the body - but they are unreliable compared to vaccines. One consistent — and broader — argument is that people who have already been infected with the SARS-CoV-2 pandemic do not need the vaccine. I think infection elicits immune responses similar to vaccines. So why waste valuable doses of the vaccine on people who already have an immune response to the virus — which may also needlessly expose them to the vaccine's side effects, albeit rare?

This is a reasonable question and there is a legitimate scientific debate about it. There are also different approaches to this issue in terms of public health policy. In Israel, for example, people who have recovered from a COVID-19 PCR test can get the Green Pass vaccination, which is valid for up to six months. This permit allows them to enter different places, just like people who have been fully vaccinated. In the European Union, some member states issue a "Digital COVID Certificate" to people who have recovered from COVID-19 and have received only one dose of the two-dose mRNA vaccine.

However, in the United States, public health officials are unequivocal in their approach: people are classified as vaccinated or unvaccinated, regardless of previous infection. This approach has many strengths, including strong scientific data that supports vaccination for people who have recovered. These data - which we will discuss below - have consistently shown that immune responses to natural infections are highly variable, so they are unreliable. On the other hand, vaccines have been shown to produce highly protective immune responses. Vaccines are also remarkably safe, with some serious side effects that only occur very rarely. One of the most important side effects is myocarditis (inflammation of the heart muscle). But even there, rates of myocarditis in high-risk groups (men aged 12-29) are estimated at only 41 per million, and cases are generally mild.

Compared to true infection with COVID-19 - which can cause severe illness even in young, healthy people and may result in persistent, monthly symptoms in half of people - there is no sweat. Vaccines are safer. It is completely safe for people who have already improved. People who have had COVID-19 before have fewer serious side effects from the vaccine than people who have never been infected, although they may have more side effects.

The American approach also has logistical benefits. The simple 'vaccinated' and 'unvaccinated' categories go through a difficult and difficult stage in determining who is infected and when. Since the early stages of the epidemic, the United States has been trying - and still trying - to conduct extensive and comprehensive testing for SARS-CoV-2. Many infected people have never had a positive official test. Others think they've become infected if they have had one of the other respiratory infections. Also, antibody tests that look for evidence of previous infection are very inaccurate.


Although opponents argue that mass vaccination is carried out by "evil companies" to make huge profits at any cost, the truth is that vaccines are very safe and provide powerful protection for those who have recovered. The virus that has killed more than 700,000 Americans so far. The American approach, on the one hand, may make vaccines look bad. In many cases, the effectiveness of a vaccine is measured by comparing cases of COVID-19 between vaccinated and unvaccinated people. But in the United States, the unvaccinated includes people who have no immunity, and people who have improved some immunity and are therefore expected to have fewer infections. This reduces the number of cases in the unvaccinated group and ultimately reduces the estimated efficacy of the vaccine.

However, the estimation of the efficacy of the vaccine is very good. A recent study showed that the Pfizer-BioNTech mRNA vaccine was 90% effective in hospitalizing COVID-19 for at least six months. A separate study showed that the Moderna mRNA vaccine was 93% effective in treating non-immunocompromised people. The Johnson & Johnson vaccine was 71% effective. And again, this may mean that you have to spend on these operations. How much less? It is not clear. Since the beginning of the epidemic, researchers have repeatedly observed that the immune responses caused by SARS-CoV-2 infection are very different, with some weaker responses in people with mild disease and stronger responses in people with severe disease.

In a study published by Ars in June of last year, researchers examined SARS-CoV-2 antibodies in people who had recovered and found that the difference between higher and lower levels was up to 1,000-fold different. . The researchers found greater diversity in neutralizing antibodies - those known to bind to the virus and prevent cell infection. Levels of neutralizing antibodies varied within the 40,000-fold range in recovered subjects, and up to 20% of subjects had no detectable level of neutralizing antibodies.


Of course, antibodies are not the sum of the immune responses that determine whether or not a person is infected, and if so, how severe the infection is. However, antibodies can provide a reasonable measure of protection for a person. A study late last year that monitored 12,500 health care workers found that the higher the level of antibodies, the lower the risk of infection. And in May this year, researchers found a "very strong" relationship between "neutralizing antibodies and vaccine protection."

The main difference between the immune responses produced by vaccines and natural infections is their quality. In a normal infection, all SARS-CoV-2 viruses infect cells of the respiratory tract. The immune cell response can target either side of these viruses. This results in a relatively large group of antibodies that bind to different components of SARS-CoV-2. On the other hand, vaccines serve only the main components of the SARS-CoV-2 immune system, which is the spike protein of the virus. It is a protein that SARS-CoV-2 uses to enter human cells and is primarily intended to neutralize antibodies. All vaccinated antibodies target the spike protein. Although vaccines have a lower antibody diversity than previously infected people, they contain higher levels of targeted antibodies. Think of it as the difference between hunting a small virus with a sniper rifle and a sniper rifle.


With altered immune responses after infection, changing real-world data is provided on how previous infections are protected from re-infection. It led to different approaches to public policy. In an online study conducted at the Cleveland Clinic in June, researchers found that among 52,238 employees, there was no difference in COVID-19 cases between employees who had not been vaccinated but had previously been infected, vaccinated and had previously been infected. There are no people who have not been vaccinated before. Infection The authors conclude: "People with SARS-CoV-2 infection are less likely to benefit from the COVID-19 vaccine." Researchers examined the vaccination status of more than 200 Kentucky residents who tested positive for SARS-CoV-2 in 2020 and tested positive again in May and June 2021. Previously infected people were re-infected and fully vaccinated. Delta difference

The time frame of the CDC study coincides with an increase in the type of delta coronavirus in the United States, which may also play a role in levels of protection against previous infection. In a French study published in Nature in July, researchers tested antibodies in 56 non-immunized people who had recovered from SARS-CoV-2 infection before delta appeared. Six months after infection and amid increased deltas, the researchers found that their neutralizing antibody levels were four to six times lower than their predecessors.

The researchers examined another group. Among 42 patients infected with SARS-CoV-2 for 1 year. Of those 42, 26 have not yet been vaccinated and 21 have received a single dose of the vaccine. At that time, 26 non-immunized had very low levels of neutralizing antibodies to SARS-CoV-2 strains, especially delta. Many people did not have detectable levels of delta neutralizing antibodies. Meanwhile, the vaccinated group had high levels of neutralizing antibodies similar to or higher than those of the fully vaccinated people.

This result has been proven in several studies. For example, a study conducted by researchers in Washington State in March found that a single dose of an mRNA vaccine in people who recovered increased the level of neutralizing antibodies against all types of SARS-CoV-2 by up to a thousand times. Several other studies showed that the dose of the vaccine after infection increases the level of antibodies in the sky. Some data also show that the level of enhanced antibodies in people who have been vaccinated is even higher than in people who have just been vaccinated. With a very safe and highly effective vaccine, a strong case for vaccinating people has been made.

Previous Vaccine Infections: Why Everyone Should Get the COVID-19 Vaccine
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