SARS-CoV-2 Reinfection Is Rare but Possible

Reinfection with SARS-CoV-2 is rare but possible, according to recent studies. Although it appears that antibodies from SARS-CoV-2 may provide some immunity for an uncertain period of time, a few cases of reinfection have been documented, says Frank Esper, MD, an infectious disease expert at Cleveland Clinic Children’s.

“Several case reports emerged within a few months of each other, beginning with one from Hong Kong,” states Dr. Esper.

The first documented case of SARS-CoV-2 reinfection

The report from Hong Kong, published in August, describes a second SARS-CoV-2 infection in an otherwise healthy 33-year-old male. The patient had a positive RT-PCR test on March 26, 2020. His symptoms included cough, sore throat, fever and headache, and resolved over a few weeks. He had two negative RT-PCR tests. After a period of 142 days, the patient was tested again to gain readmission to Hong Kong following European travel. This test was positive. During this second infection, the patient was asymptomatic.

Dr. Esper believes this was a true reinfection. “Genetic profiling found that the viruses were completely different strains. Additionally, there were negative tests in between the positive ones. Combined, this makes a strong case for reinfection,” he says.

Distinguishing reinfection from prolonged viral shedding

Shortly after the Hong Kong case was published, researchers in Belgium described the case of a 51-year-old-woman who developed a symptomatic reinfection 93 days after her first infection. In the first infection, she had moderate but persistent symptoms, and a positive RT-PCR. She did not require hospitalization, but did stay home from work for five weeks due to her symptoms. Three months later, she experienced a relapse with milder symptoms. Her RT-PCR was positive. Genome sequencing confirms that the infections different strains of SARS-CoV-2. This time, her symptoms resolved in about a week.

Last month, a South American case was posted describing a 46-year-old male with mild symptoms and a positive RT-PCR. Following symptom resolution, his RT-PCR was negative. More than one month later, after close contact with relative who was COVID-19 positive, this patient again developed symptoms and had a positive RT-PCR. This time the symptoms were more severe, including odynophagia, congestion, fever, back pain, cough and dyspnea. His clinical status improved over the next several weeks.

Lastly, in mid-October, evidence was presented of a reinfection case from Nevada. The patient was a 25-year-old man with mild viral symptoms and a positive RT-PCR on April 18. His symptoms resolved within 10 days, and a RT-PCR from May 26 was negative. On May 31, he sought care for recurring symptoms that progressed and required hospitalization for hypoxia with shortness of breath on June 5, at which point an RT-PCR was again positive for SARS-CoV-2. Genome sequencing revealed that the viruses were from the same strain; however, there were so many differences between the two that researchers concluded it couldn’t have been an evolution of the original infection.

“Distinguishing between prolonged viral shedding and reinfection is a problem we are still trying to work out,” Dr. Esper explains. “Early in the pandemic, we thought that the infection might take a couple weeks to clear, and that patients would test negative at that time. We realized very quickly that people can be positive for a very long period of time, at least partly because we’ve designed the tests to be quite sensitive. People who have a second positive test spread out by more than a month, with negative tests in between, and had developed new symptoms after their symptoms of the first infection have resolved, may in fact be reinfections. Genetic analysis that reveals different viral strains makes a case even stronger.”

Viruses mutate

It is not abnormal to see mutations during the course of a person’s viral illness, according to Dr. Esper. But we don’t have enough data about what SARS-CoV-2 does during an infection.

“How does the virus mutate after 10 days? After 30 days in a person? And does that change depend on the immune status of a person?” Dr. Esper asks. “These are questions that still have yet to be answered.”

SARS-CoV-2 appears to be mutating very slowly compared to other common viruses like influenzas or rhinoviruses. “This is actually good news. If the body has an effective, antibody-producing response, this should provide protection for a longer period of time.”

Preventive measures are important, whether you’ve had COVID-19 or not

This doesn’t mean that previously infected individuals should be considered safe, Dr. Esper cautions. “We expect immunity will wane in people who have been infected, but we don’t necessarily know how long that would take. We’re not seeing tremendous numbers of reinfections, which suggests that the immune response may last a while. But it’s very important to stress to patients that reinfections can happen – and that the symptoms of reinfection may be different than the first bout of illness. It is quite possible that a reinfected person may be less symptomatic or asymptomatic and still shed the virus, infecting their friends and loved ones.”

“It is just way too early for people to stop practicing preventive measures. We all need to come together to prevent future infections, especially now when the numbers are skyrocketing. Most people at this point have still not been infected; most people remain susceptible. With a vaccine on the horizon, we don’t want to stumble at the finish line. We need to keep up everything that we’re doing – wearing face masks, washing our hands, and maintaining physical and social distance – while we wait for researchers to establish the safety and efficacy of the vaccine, and ramp up production distribution,” Dr. Esper concludes.