COVID-19: What is the risk of reinfection?

A few studies have assessed immunologic changes during and after a COVID-19 infection. Some results have suggested that neutralising antibodies are protective. At the ERS 2020 Congress, Prof. Peter Openshaw (Imperial College of London, UK) reviewed some immunological considerations from recent COVID-19 studies [1].

“What we know about this virus is just changing from hour to hour,” said Prof. Openshaw. A few initial studies from China have shown a neutralising antibody response to SARS-CoV-2 in a patient cohort that recovered from COVID-19 [2]. The results suggest that there is more antibody production in patients with severe disease. Unfortunately, asymptomatic individuals have a weaker immune response to SARS-CoV-2 infection, as shown by a Chinese study in 37 asymptomatic individuals [3]. This study assessed the clinical features and immune responses of asymptomatic patients with a SARS-CoV-2 infection and found that 81.1% of the 37 asymptomatic participants showed declining neutralising antibodies in the convalescent phase, compared with 62.2% of symptomatic participants. 40% of asymptomatic individuals became seronegative compared with 12.9% of the symptomatic group. Interestingly, duration of viral shedding was longer in asymptomatic individuals compared with those with symptoms. Moreover, asymptomatic individuals exhibited lower level of 18 pro-inflammatory and anti-inflammatory cytokines.

In the United Kingdom, the ISARIC-4C (Coronavirus Clinical Characterisation Consortium) cohort collected data from COVID-19 patients. Up to July 2020, demographic data, outcomes, and comorbidities of 64,323 patients were collected (Tier 0). Single biological samples from plasma/serum, nasal swabs, urine, and stools were collected from 644 patients. Serial biological sample sets are available from another 1,625 patients. One of the first studies that came from this cohort assessed the T-cell response during infection with COVID-19 in 28 patients with mild disease and 14 with severe disease [4]. This study showed that memory T-cell responses were greater in severe cases.

In a North America cohort, a study on the humoral immune response to SARS-CoV-2 showed that IgG, IgA, and IgM antibody responses were accurate in identifying recently infected individuals, with 100% specificity and 97%, 91%, and 81% sensitivity, respectively [5]. IgA and IgM antibodies were short-lived. IgG antibodies lasted longer and persisted through 75 days post-symptoms. The authors concluded that IgG antibodies are correlated with neutralising antibodies and are possibly a correlate of protective immunity. A study on the outbreak of SARS-CoV-2 on a fishing vessel further showed that the presence of high neutralising antibodies was associated with protection (P=0.002) [6]. “This finding is important because it tells us that the presence of antibodies is protective,” Prof. Openshaw said.

Taken together, these results show that a COVID-19 infection primes B and T cell immunity. “It is not clear whether the protection by viral infection stays more than a few months, but vaccines may possibly induce better immunity than natural infection,” Prof. Openshaw concluded.

 

1. 
   
   1. Openshaw P. Immunology underpinning vaccine strategy: what is the risk of reinfection? COV3619, ERS International Virtual Congress 2020, 7-9 Sept.
   2. Wu F, et al. Preprint at medRxiv.Doi:10.1101/2020.03.30.20047365.
   3. Long QX, et al. Nat Med 2020 Aug;26(8):1200-1204.
   4. Peng Y, et al. Nat Immunol. DOI:10.1038/s41590-020-0782-6.
   5. Iyer AS, et al. Preprint at medRxiv. Doi:10.1101/2020.07.18.20155374.
   6. Addetia A, et al. J Clin Microbiol 2020.Doi:10.1128/JCM.02107-20.

 



Posted on 29 October 202023 February 2021