COVID-19 reinfection among health care workers in a tertiary care center in north Kerala: a descriptive study

INTRODUCTION

COVID-19 is an infectious disease caused by Severe Acute Respiratory Corona Virus-2 (SARS-CoV-2). It, binds to the angiotensin-converting enzyme 2 receptors using a receptor-binding domain in its spike protein for cell entry and ultimately, resulting in a respiratory syndrome.^1,2 COVID-19 was declared as global pandemic by WHO on March 11 2020. Approaches to control COVID-19 depend on the durability of immunity conferred by recovery and by vaccination. However, predicting the durability of immunity against the virus causing COVID-19, SARS-CoV-2, remains challenging amid a pandemic.³ Reinfections are observed with many respiratory viruses, including human coronaviruses. Reinfections with respiratory viruses may be due to weak or waning initial immune response (e.g., respiratory syncytial virus), reinfection with another genotype/species (e.g., rhinoviruses) or the high variability of the viruses (e.g., influenza virus).⁴

Reinfection was defined as any reverse transcription polymerase chain reaction (RT‐PCR) or antigen‐confirmed SARS‐CoV‐2 infection in an individual with evidence of a prior SARS‐CoV‐2 infection. Evidence of prior infection included a prior SARS‐CoV‐2 diagnosis by RT‐PCR or antigen testing followed by recovery (molecular or clinical evidence of viral clearance). No minimum time interval was defined between primary and secondary infections; however, cases within 90 days of initial infection were considered suggestive of prolonged viral shedding following the primary infection.⁵ Centres for Disease Control and Prevention (CDC) has considered the duration of 90 days between two positive SARS-CoV-2 RNA along with genomic evidence of re-infection as an investigative criterion to understand the phenomenon of re-infection.⁶

Re-infection rate is likely to be a significant threat to the current measures to control the COVID-19 pandemic. Understanding the protection conferred by previous infection against repeat infection, illness, and severe disease is key to projecting the future epidemiology of COVID-19 and to guiding vaccine policy decision.⁷ Prevention, identification, and management of these patients will be essential to avoid mortality as re-infection can be severe.⁸

Aim of study were to determine the proportion of SARS COV-2 reinfection among health care workers in a tertiary care center in north Kerala and to determine the meantime interval between primary infection and reinfection. Also, to study the symptoms during primary infection and reinfection.

METHODS

A record based descriptive study was conducted among health care workers in a tertiary care centre in north Kerala. All health care workers who tested positive for COVID-19 during 1^st July 2020 to 31^st October 2021 were included in the study which accounted for 704 cases.

Operational definition

Covid -19 case: A person with laboratory confirmation of COVID-19 infection either by molecular test or rapid antigen test.

Covid-19 reinfection: An individual who tested positive for SARS COV-2 on two separate occasions either by molecular test or rapid antigen test separated 90days apart.

Data collection and analysis

Data regarding COVID-19 positive healthcare workers was collected from Regional Prevention of Epidemic and Infectious Diseases cell (RPEID) data base. Data regarding symptoms was collected from individual study subjects by telephonic interviews. Data was entered in MS Excel and analyzed using SPSS version 21.

RESULTS

Demographic profile

Of the 704 HCW who tested positive for COVID-19 during the study period, 36 (5.11%) met the criteria for reinfection. Mean age was 29.6±9.7years (Figure 1).

Symptomatology

During primary infection 36% were asymptomatic compared to 3% during reinfection. During reinfection majority (97 %) were symptomatic (Figure 2).

Mean symptom duration during primary infection was 2.3 days. Mean symptom duration during reinfection was 5.08 days. Mean time interval between primary infection and reinfection was 244.6±75.6 days (113-427 days) (Figure 3).

Of the 36 cases of reinfection, 4 (11.1%) had symptoms during the time interval between primary infection and reinfection. All 4 had breathlessness during that time period between primary infection and reinfection. Among the reinfected cases 4 (11.1%) had comorbidities, of which 2 had type 2 diabetes mellitus, 2 had hypothyroidism, 1 had bronchial asthma (not mutually exclusive) (Table 1, 2).

DISCUSSION

Study was conducted among 704 Health care workers who tested positive for COVID-19. In the current study 5.11% met the criteria for reinfection which was like study by Mukherjee et al in which 4.5% met the criteria for reinfection.⁹ In a retrospective cohort study conducted by Sheehan et al and Akinbami et al reinfection rate was found to be 4.8% and 2.5% respectively.^10,11 In a cohort study by Slezak et al cumulative incidence of reinfection was 0.8 %.¹²

Mean age of the study population was 29.6±9.7years it was similar to study by Mukherjee et al.⁹ In a systematic review by Dhillon et al mean age of patients was 46.2+/-18.9 years.¹³

Mean time interval between primary infection and reinfection was 244.6±75.6 days compared to 119 days in the study conducted by Mukherjee et al and 3-6 months in study by Islam et al.^9,14

In the current study majority (77.8 %) were unvaccinated during primary infection compared to 8.3% during reinfection. At the time of reinfection 80.6% were vaccinated with 2 doses of COVID-19 vaccine.

In the study by Mukherjee et al, large proportion of the respondents were asymptomatic during the first episode (47.4%) as compared to the second one (15.8%).⁹ This was similar to the current study in which a large proportion (36%) was asymptomatic during primary infection compared to a small proportion (3%) during reinfection.

In the current study mean symptom duration during primary infection was 2.3 days compared to 5.08 days during reinfection. In the study conducted by Sheehan et al, hospitalization was more common at suspected reinfection (11.4%) than initial infection (5.4%).¹⁰ In a systematic review by Jingzhou et al, 68.8% had similar severity during reinfection while 18.8% and 12.5% had worse and milder symptoms respectively.¹⁵

Most common symptom during primary infection and reinfection was fever, it was similar to study by Dhillon etal.¹³ During the time period between primary infection and reinfection majority were asymptomatic only 11.1% had symptoms. This was like study by Mukherjee et al in which 71.1% were asymptomatic during time period between primary infection and reinfection.⁹

Since the current study is a hospital based study reinfection rates obtained cannot be generalized to the community. The current study is a descriptive study and serological evidences are lacking, further serological studies must be conducted for the confirmation of existence of COVID-19 reinfection.

CONCLUSION

Reinfection is possible in individuals who had primary infection with COVID-19. Reinfection can be symptomatically more severe compared to the primary infection even in vaccinated individuals. So regardless of previous history of infection with COVID-19 all individuals must strictly adhere to Covid protocol.

ACKNOWLEDGEMENTS

We would like to thank all the interns who actively helped in data collection and to all teaching staffs in the department of Community Medicine who gave their valuable feedback during various stages of the study. Authors also would like to thank all the RPEID cell staff for their support and help during the study.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

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