Revealing COVID-19 breakthrough infection rates among vaccinated individuals at a tertiary care centre in South India

Vanathy  Kandhasamy; Ramya  Priyadarshini; Namrata Krishna  Bhosale; Raji Ramachandran  Pillai; Malarvizhi  Ramalingam; Agiesh Kumar  Balakrishna Pillai; Ezhumalai  Govindasamy; Joshy Maducolil  Easow

doi:10.18502/ijm.v17i2.18380

Vanathy Kandhasamy Department of Microbiology, Mahatma Gandhi Medical College & Research Institute (MGMCRI), Sri Balaji Vidyapeeth (Deemed to be University), Pondicherry, Puducherry, India
Ramya Priyadarshini Department of Microbiology, Mahatma Gandhi Medical College & Research Institute (MGMCRI), Sri Balaji Vidyapeeth (Deemed to be University), Pondicherry, Puducherry, India
Namrata Krishna Bhosale Department of Microbiology, Vinayaka Mission's Medical College and Hospital, Vinayaka Mission’s Research Foundation (Deemed to be University), Karaikal, Puducherry, India
Raji Ramachandran Pillai Department of Microbiology, Mahatma Gandhi Medical College & Research Institute (MGMCRI), Sri Balaji Vidyapeeth (Deemed to be University), Pondicherry, Puducherry, India
Malarvizhi Ramalingam Department of Microbiology, Mahatma Gandhi Medical College & Research Institute (MGMCRI), Sri Balaji Vidyapeeth (Deemed to be University), Pondicherry, Puducherry, India
Agiesh Kumar Balakrishna Pillai Department of Virology, Scientist F, Advanced Institute of Virology, Trivandrum, Kerala, India
Ezhumalai Govindasamy Department of Deanery Research, Sri Balaji Vidyapeeth (Deemed to be University), Pondicherry, Puducherry, India
Joshy Maducolil Easow Department of Microbiology, Mahatma Gandhi Medical College & Research Institute (MGMCRI), Sri Balaji Vidyapeeth (Deemed to be University), Pondicherry, Puducherry, India

DOI: https://doi.org/10.18502/ijm.v17i2.18380

Keywords: Breakthrough infections; SARS-CoV-2 virus; COVID-19; Vaccination; Outbreak

Abstract

Background and Objectives: The COVID-19 pandemic was mitigated by the rapid development and deployment of vac- cines. While vaccines reduce infection severity, breakthrough infections (BTIs) still occur. The CDC defines BTI as a pos- itive SARS-CoV-2 test ≥14 days post-vaccination. This study investigates the occurrence of COVID-19 BTIs at a tertiary care hospital in Puducherry, South India.

Materials and Methods: This retrospective study analysed hospital tested qRT-PCR data of individuals from the ICMR

portal (March 2021–March 2022). Demographic and vaccination details were extracted.

Results: Among 8001 tested individuals, 1452 were vaccinated. The BTI rate decreased from 16.6% to 1.2% after the first dose and from 58% to 40% after the second one. Odds ratio indicated a 74% reduction in infection risk for vaccinated indi- viduals compared to unvaccinated. Males had higher infection rates than females, regardless of vaccination status.

Conclusion: Our study demonstrates a higher BTI rate after one vaccine dose compared to two doses. The BTI rate also increased four months post-vaccination, even with two doses, potentially due to waning immunity and the emergence of new variants. Therefore, continued adherence to preventive measures in conjunction with vaccination is crucial for minimizing COVID-19 transmission.