Can You Get COVID More than Once?

More than 48 million Americans have been infected with COVID-19 since the pandemic began in 2020. As more time passes and immunity begins to wane, many Americans are wondering if they can get COVID-19 more than once, also known as COVID reinfection.

To help answer these questions, we explain the differences between natural immunity and vaccine-induced immunity, why you should still get the vaccine even if you've previously had COVID and shed more light on reinfection and breakthrough cases.

How do viruses infect cells?

By now, COVID-19 has taught Americans just how deadly viruses can be. While it’s easy to focus on the end result — severe illness, hospitalizations and death — many steps must occur for an infection to happen.

Viruses, like the coronavirus, are made up of genetic code (either DNA or RNA) protected by a protein coating. Viruses can’t replicate on their own. In other words, they need a host to cause an infection. The host is typically animals or humans, in which the virus finds cells and injects them with their genetic material. The virus then makes copies of these cells which cause damage to your body.

As viruses replicate, the immune system initiates a response. Your body contains lymphocytes, a type of white blood cells that defends against bacteria, viruses, parasites and fungi. These lymphocytes mainly come in the form of B cells and T cells. First, T cells destroy the body’s own cells that have become infected by the virus. Then B cells take over to produce antibodies that also attack the virus.

Once the infection is over, antibodies remain to fight against future infection. How long these antibodies stay present is what researchers have studied since the inception of COVID-19.

COVID reinfection rate

Reinfection occurs when you become infected, recover from the virus, and then become infected at a later date.

While there have been COVID-19 reinfection cases, they remain rare, according to the Centers for Disease Control and Prevention. Just this past summer, reinfection cases made up less than 1% of total COVID-19 cases, according to one study by the University of Missouri School of Medicine. A review of more than 9,000 Americans showed a reinfection rate of 0.7%, with an average reinfection time coming 3 ½ months following a first positive test.

However, the accuracy of these figures is somewhat unclear. For starters, it can be difficult to track reinfection rates because many COVID-19 cases are mild and people may never know they had it again. Plus, some reinfection cases may be confused with trace amounts of the virus remaining in the body and triggering subsequent tests. For example, the coronavirus can shed virus for several months. This doesn’t mean a new infection has occurred, rather, the original infection has yet to exit your body.

The reality is no immunity or vaccine is ever 100 percent effective, so there are bound to be people who get COVID-19 for a second time. As Americans experience more and more COVID fatigue, reinfection rates are likely to increase due to waning immunity and a lax in safety measures such as wearing masks and social distancing.

So far, that is the case in Oklahoma. The state health department no longer produces weekly updates regarding reinfection rates or breakthrough cases, but figures from September showed the rate of reinfection (1,093.8 per 100,000 cases) was twice as high as breakthrough cases (557.4 per 100,000 cases). In just two months, the reinfection rate doubled from 512.8 this past August to 1,093.8 in September.

What is a COVID breakthrough case?

You may have heard or seen the word COVID breakthrough case recently. This new term is used to describe reinfection in people who have been vaccinated. Yes, vaccines prevent infection for most people, but there is always a small chance you can still become infected, hence the name breakthrough.

The chances of experiencing a breakthrough case after becoming vaccinated are low, according to data from this past year. A study of 4 million fully vaccinated people determined there was a 1 in 5,000 chance of a breakthrough infection. Other studies are closer to 1 in 100, or 1 percent. 

Inevitably, these figures vary depending on the state and region where COVID cases are more prominent than other areas. In New York where COVID was a hotbed for cases in 2020, there have been more than 175,000 confirmed breakthrough cases, which accounts for 1.4 percent of people aged 12 and over who are fully vaccinated. Likewise, in Virgina, the rate of infection from January 2021 to November 2021 was 1.15 percent for fully vaccinated people.

The goal of vaccines isn’t necessarily to outright prevent COVID infections. Instead, it’s to reduce the seriousness of the infections and limit hospitalizations and death. In the case of breakthrough infections, fully vaccinated people tend to experience symptoms that are less severe and with a shorter duration. 

It’s important to remember people with breakthrough cases, even if less severe, are still contagious. You can be asymptomatic and carry the virus without realizing it, allowing unvaccinated people to become infected. This is why washing your hands and wearing a mask in public are still two critical steps to reducing the transmission of COVID-19.

COVID immunity after infection

Immunity, from a general perspective, is a state in which your body remembers the pathogens and foreign invaders (in this case the coronavirus) to be better prepared in the event of reinfection.

Initially, antibodies were believed to last around three to four months, according to a study by the National Institutes of Health in late 2020. Others believed this number to be in the 90- to 180-day range.

Regardless, the term immunity is subjective because it can vary by person. One person may have months of immunity, whereas someone else may enjoy more than a year of immunity. New variants of the coronavirus can also play a role. Viruses can mutate and become resistant to certain aspects of vaccines, thus reducing the length and effectiveness of your immunity.

Immunity from some other coronaviruses, like the one that caused Middle East Respiratory Syndrome (MERS), has been shown to last years. Immunity from COVID-19 is less clear, primarily due to the research being gathered — researchers tend to study people with moderate to severe COVID symptoms. However, this information doesn’t apply to the majority of Americans since most cases are mild or remain asymptomatic.

While experts continue to analyze the longevity of COVID immunity, a research study conducted by the Yale School of Public Health found the COVID-19 immunity to be short — 50 percent reinfection risk after 17 months. The study was an estimate by using previous analysis from related viruses such as SARS-CoV, MERS-CoV and several other coronaviruses that cause the common cold.

An additional study found a prior COVID infection reduced your risk of reinfection by 80 percent for six months. However, this number was just 47 percent for adults 65 and older.

Should I get the COVID vaccine if I had COVID?

Yes, immunity only lasts so long. It’s better to protect yourself and others around you by receiving the vaccine. This is due to the fact that vaccine-induced immunity is believed to be higher than natural immunity.

Natural immunity vs. vaccine

Natural immunity has become a popular topic of late, but the truth is this type of immunity varies by person and the type of pathogen. For example, people who become infected with measles are unlikely to ever get it again due to a strong antibody reaction that creates long-lasting immunity.

As more and more research is conducted, natural immunity from COVID-19 is believed to weaken and isn’t as strong as immunity from the vaccine. As more time passes, the greater the chance the genetic material in the coronavirus is able to overcome host immunity and lead to reinfection.

There is also data that shows a relationship with being unvaccinated and higher reinfection rates. The CDC published a study last summer that found unvaccinated people were 2.34 times more likely to become reinfected, meaning receiving the vaccine lowers your risk of getting COVID-19 a second time.

An additional study found unvaccinated people who previously had COVID were 5.49 times more likely to become hospitalized due to reinfection than people who had been vaccinated for COVID with no previous history of infection.

If anything, a previous COVID infection, when combined with a full vaccine dose, allows for longer-lasting antibody levels, according to a large study conducted by Johns Hopkins. In a study of more than 1,900 people, antibodies levels increased as time went on following two vaccine doses — 14 percent at one month, 19 percent at three months and 56 percent at six months. This is even more of a reason why you shouldn’t skip your second COVID vaccine.

The COVID-19 vaccine contains messenger RNA (mRNA) that triggers a target immune system response. Once injected, the mRNA teaches the immune system how to create antibodies that protect against COVID.

To learn more about COVID-19, visit our COVID-19 resource page. Learn more about COVID-19 vaccines here, or schedule a vaccination appointment by visiting Oklahoma State Department of Health’s website.