What is the difference between the immunity you develop from getting COVID-19 and immunity from getting a COVID-19 vaccine?

It has been more than 2 years since the Covid-19 first broke out in Wuhan, China. To date, more than 500 million of the world’s population have been infected with the virus [1]. As the infection rates continue to climb and vaccination programs are continuously rolled out, we wonder if there is a difference between the immunity from the infection itself and the immunity obtained from the vaccines. This article summarizes the evidence from the Centers for Disease Control and Prevention (CDC), which looked at the immune responses developed from both infection and the vaccine, how long the immunity lasts, and whether the infection or immunity provides better protection from reinfection.

Immune Response

When we consider an immune response, we consider the antibodies produced towards the antigen. Antibodies are created by our own immune system to fight the antigen, and they have the ability to recognize future infections and protect us against the same pathogen. Antibodies can be produced via natural infection, or they can be induced by vaccines. As a general rule, the more and the longer lasting these antibodies are, the stronger the immunity is towards the infection.

The Covid-19 causative virus, SARS-CoV-2, has a signature spike protein that helps it invade our cells and cause an illness. In a natural infection with the virus, our bodies start to produce antibodies around 5-15 days following a confirmed infection, or from the onset of symptoms [2]. These antibodies reach a peak and gradually fall after 2-3 months, albeit still detectable. Studies found that more severe infection generally leads to higher levels of antibodies. Similar studies look at the immune response the body developed with vaccines, including Pfizer-BioNTech, Moderna, and Janssen. These studies found that the completion of 2 doses of the vaccines leads to higher antibody levels that are more consistent over time [2].

Similarly for both, people who are immunocompromised or have a weakened immune system (autoimmune disorders, cancers, etc.) generally have a lower antibody production ability, regardless if it is from the vaccine or the infection,

Protection from reinfection or severe illness

Based on cohort studies conducted among health care workers, a previous infection provided 84% protection against re-infection. Other studies carried out in various countries involving large populations also found that a confirmed infection decreases the risk of infection by 80-93% (similar to the study mentioned earlier), and the protection can last for at least 6-9 months. Follow-up studies are still in place to see if the protection could last longer than that.

On the contrary, studies on vaccines look at the protection of vaccines against severe diseases and found promising results. It was validated that vaccines protect individuals against hospitalizations and severe illnesses up to 84-96% [2]. Although the immunity after vaccination declines over time, this 84-96% protection can last for at least 6 months. This is why booster vaccinations are recommended. Indeed, many countries have relaxed their prevention measures for the pandemic as vaccination rates continue to increase, and the burden of disease significantly falls.

Protection from different corona strains

Many wonder if the vaccines could provide protection despite the various strains of SARS-CoV-2. There are inadequate studies done to observe this. In the United Kingdom, a survey found that fully vaccinated adults are protected against the virus during the Alpha predominant season (79% protection).

All in all, there is no significant difference between the protection provided by natural infection and vaccination. However, it is definitely worthy to note that vaccines have successfully reduced the risk of hospitalization and severe illness. There is also increasing evidence to show that the antibody titers in people who received the vaccination after infection are significantly higher [1]. It is therefore recommended for people to get the covid-19 vaccination right away after the infection has passed.

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