COVID-19 Reinfection

After the first case was discovered in Wuhan, China, in 2019, COVID-19, caused by the Severe Acute Respiratory Syndrome Virus-2 (SARS-CoV-2), quickly spread around the world. Two years later, even as COVID-19 cases have been dropping around the world, the level of reinfection continues to influence public health and attracts the attention of academics.

According to the CDC, “reinfection with the virus that causes COVID-19 means a person was infected, recovered, and then later became infected again. After recovering from COVID-19, most individuals will have some protection from repeat infections. However, reinfections do occur after COVID-19.”

The risk of reinfection is expected to vary depending on a variety of circumstances. The WHO estimates the previous infection only gives a protection level of 50% in the over-65 population. Reinfection risk is believed to be influenced by several factors, including:

• The risk of contracting COVID-19 from other persons
• Whether you’ve been vaccinated against COVID-19 — data suggests that reinfection is higher in unvaccinated people and perhaps those who had a milder initial infection with a weaker immune response
• Individual characteristics (such as underlying health conditions)

Occurrence of COVID-19 Reinfection

Despite the presence of antibodies, reinfection by various human coronaviruses is common. According to the WHO, the presence of antibodies in recovered patients does not guarantee protection from reinfection. They state:

“Four large studies from the United Kingdom, the United States of America, and Denmark estimated that infection with SARS-CoV-2 provided 80–90% protection from reinfection for up to 7 months and up to 94% protection against symptomatic disease. The level of protection against reinfection as assessed by PCR positivity was estimated to be 50% in people aged over 65 years old.”

On its COVID-19 dashboard, the United Kingdom shares statistics on reinfections. There have been about 14.5 million primary infections in England and around 620,000 reinfections up until February 6, 2022, indicating one reinfection for every 24 primary infections.

The New York State Department of Health (NYSDOH) has also established a dashboard with statistics on COVID-19 reinfection in New York State to provide the public with continuing information on reinfections. There have been about 5.5 million primary infections in New York and 283,000 reinfections, indicating one reinfection for around every 20 primary infections.

Reinfection With Variants

The newest variants, according to research, are also more effective at evading immune defenses and antibody treatments than the original strain.

Data on reinfections and new infections are provided separately because they are collected through various methods. For example, in New York, The COVID-19 daily testing tracker and the positive tests over time dashboard display the number of new infections in New York State based on when they are reported to the state. The reinfection page shows how many times a person has tested positive, including those who have tested positive 90 days or more after their first positive test.

COVID-19 Reinfection with Delta Variant

The WHO has categorized the Delta variant of COVID-19 as a variant of concern (VOC) due to its increased transmissibility and tendency to induce a severe version of the disease. When the Delta variety enters a population, it spreads swiftly and efficiently among people.

A Lancet surveillance study suggests that the risk of reinfection with SARS-CoV-2 is highly linked to community infection rates, particularly during the Delta variant wave. Children had a lower probability of reinfection than adults, and reinfections were not linked to worse disease or death.

COVID-19 Reinfection with Omicron Variant (BA.1)

South Africa reported a novel SARS-CoV-2 strain, Omicron to WHO on November 24. This variant was identified as a “variant of concern” (VOC) and named Omicron, and is now also referred to as Omicron BA.1.

A South African study published in 2022 found the likelihood of reinfection during the recent Omicron wave was significantly higher than during the country’s previous Beta and Delta surges.

Additionally, a growing number of people in the United States may be at risk of reinfection. In the CDC Morbidity and Mortality Weekly Report (MMWR)for April 15th, 2022, approximately half of these reinfections occurred during the Omicron-predominant wave. This is concerning as a number of these reinfected people may develop the disease to a level requiring hospitalization.

In the report, COVID-19 mRNA immunization was found to confer protection against recurrent COVID-19–related hospitalization in people who had previously been infected with the virus. During the Omicron-predominant era, vaccine efficacy against reinfection leading to hospitalization was estimated to be around 35% after the second dose and 68% after a booster dose.

COVID-19 Reinfection with Omicron BA.2 subvariant

Researchers from Denmark recently examined the BA.2 variant’s reinfection risks, looking into whether the BA.2 variant can infect patients who have already been infected with the omicron variant.

BA.2 is currently the most common cause of Covid-19 in Denmark. The researchers, from Denmark’s Statens Serum Institut, looked at 140,000 viral genomes from infected patients. A total of 263 reinfections were discovered. The findings revealed 47 people who had been reinfected with BA.2 after getting the original omicron variant.

This indicates that BA.2 can reinfect people who have already had other COVID-19 infections, such as Omicron BA.1, but that it is rare.

The most protection against reinfection by BA.2 is being triply vaccinated, as this works alongside the previous infection to boost the immune system, according to a Qatar study.

COVID-19 Reinfection Symptoms

Reinfections are typically mild, according to early research. The severity of the disease appears to be milder among individuals who are reinfected, and hospitalization is less likely. For example, according to a study conducted in Qatar, reinfection cases have a 90% lower chance of resulting in hospitalization or death than original infections.

COVID-19 reinfection symptoms differ depending on the severity of the disease caused and which strain causes the reinfection. For example, fewer people infected with the BA.2 COVID-19 variant reported a loss of smell or taste and more people reported flu-like symptoms than prior strains, according to an English study.

A meta-study, covering 20 countries, found reports of 118 cases of reinfection. The timeframe between infection and reinfection was 19 days, while the longest time was 293 days. The most prevalent symptoms during the initial infection and reinfection were cough (51.6%) and fever (50%), And 25 patients were reported to have at least one complication.

Overall, the meta-study found most reinfected patients show clinical symptoms, and only a few studies have reported patients being asymptomatic at both the first and secondary infections. The Dutch study, mentioned above, found that reinfection by the BA.2 subvariant after infection by the BA.1 subvariant usually resulted in mild symptoms that rarely required hospitalization.

However, it is challenging to assess COVID-19 severity at a population level. While some second infections were milder, this was not true in all instances, according to a systemic analysis of case reports. Reinfections led to poorer outcomes, including death in some cases.

To ascertain if reinfection is actually less severe, more studies are required.

Reinfection With SARS-CoV-2 After COVID-19 Vaccination

Kentucky’s May–June 2021 CDC MMWR reported that Kentucky residents who were unvaccinated against COVID-19 and had been previously infected with SARS-CoV-2 in 2020 were more than twice as likely to be reinfected in May and June 2021 as compared to fully vaccinated residents.

As per the findings, a completed COVID-19 vaccination program gives extra protection against reinfection in people who have previously been infected with SARS-CoV-2.

Hence, vaccination remains the best way to combat SARS-CoV-2 complications. A booster dose of COVID-19 vaccination gives the highest protection against hospitalization from reinfection. According to the CDC, all eligible patients, including those who have already been infected with SARS-CoV-2, should get vaccinated to avoid COVID-19-related hospitalization.

Conclusion

As immunity wears out or new varieties emerge, the risk of reinfection will fluctuate. Studies to discover more about COVID-19 reinfection and the length and strength of immunity that comes with it are still ongoing — the results will help give a clearer picture of incidents of reinfection.

Just as the diagnosis and treatment of reinfection should be the same as for the first infection, coughing remains the most common among COVID-19’s early symptoms.

Cough tracking is one way of keeping tabs on this symptom. If you’re a doctor, look at our cough tracking app, Hyfe. We want to hear your experience with it from you. Consider recommending the app to your patients if you find it helpful.