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COVID-19 Infection Among Women in Iran Exposed vs Unexposed to Children Who Received Attenuated Poliovirus Used in Oral Polio Vaccine

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To identify the key insights or developments described in this article
1 Credit CME
Key Points

Question  Is indirect exposure to live attenuated poliovirus in the oral polio vaccine (OPV) associated with diminished symptomatic infection with SARS-CoV-2?

Findings  In this cohort study of 4190 women in Iran, none of those indirectly exposed to OPV developed COVID-19 during the 9 months of the study, while 0.74% of age-matched women who had no exposure to OPV did develop COVID-19.

Meaning  These findings suggest that indirect exposure to live attenuated poliovirus may be associated with decreased symptomatic COVID-19 infection for at least 6 months.


Importance  Live attenuated vaccines may provide short-term protection against infectious diseases through stimulation of the innate immune system.

Objective  To evaluate whether passive exposure to live attenuated poliovirus is associated with diminished symptomatic infection with SARS-CoV-2.

Design, Setting, and Participants  In a longitudinal cohort study involving 87 923 people conducted between March 20 and December 20, 2020, the incidence of COVID-19 was compared between 2 groups of aged-matched women with and without exposure to live attenuated poliovirus in the oral polio vaccine (OPV). Participants were people receiving health care services from the Petroleum Industry Health Organization and residing in 2 cities in Iran (ie, Ahwaz and Shiraz). Participants were women aged 18 to 48 years whose children were aged 18 months or younger and a group of age-matched women from the same residence who had had no potential exposure to OPV.

Exposures  Indirect exposure to live attenuated poliovirus in OPV.

Main Outcomes and Measures  Symptomatic COVID-19, diagnosed by reverse transcription–polymerase chain reaction.

Results  After applying the inclusion and exclusion criteria, 419 mothers (mean [SD] age, 35.5 [4.9] years) indirectly exposed to the OPV and 3771 age-matched women (mean [SD] age, 35.7 [5.3] years) who had no exposure to OPV were available for analysis. COVID-19 was diagnosed in 1319 of the 87 923 individuals in the study population (151 per 10 000 population) during the study period. None of the mothers whose children received OPV developed COVID-19 after a median follow-up of 141 days (IQR, 92-188 days; range, 1-270 days); 28 women (0.74%; 95% CI, 0.47%-1.02%) in the unexposed group were diagnosed with COVID-19 during the 9 months of the study. Point-by-point comparison of the survival curves of the exposed and unexposed groups found that indirect exposure to OPV was significantly associated with decreased COVID-19 acquisition; probability of remaining without infection was 1.000 (95% CI, 1.000-1.000) in the exposed group vs 0.993 (95% CI, 0.990-0.995) in the unexposed group after 9 months (P < .001).

Conclusions and Relevance  In this cohort study, indirect exposure to live attenuated poliovirus was associated with decreased symptomatic infection with COVID-19. Further study of the potential protective effect of OPV should be conducted, especially in nations where OPV is already in use for polio prevention and specific COVID-19 vaccines are delayed, less affordable, or fail to meet demand.

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Article Information

Accepted for Publication: September 22, 2021.

Published: November 24, 2021. doi:10.1001/jamanetworkopen.2021.35044

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Habibzadeh F et al. JAMA Network Open.

Corresponding Author: Robert C. Gallo, MD, Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD 21201 (

Author Contributions: Dr Habibzadeh had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Habibzadeh, Sajadi, Chumakov, Yadollahie, Simi.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Habibzadeh, Chumakov, Stafford.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Habibzadeh, Sajadi, Yadollahie, Simi, Stafford.

Obtained funding: Habibzadeh.

Administrative, technical, or material support: Habibzadeh, Yadollahie, Kottilil, Simi, Saeidimehr, Rafiei, Gallo.

Supervision: Habibzadeh, Sajadi, Gallo.

Conflict of Interest Disclosures: Dr Kottilil reported receiving grants from the National Institutes of Health and Gilead and serving on the advisory boards of Merck and Regeneron outside the submitted work. No other disclosures were reported.

Additional Contributions: The authors would like to thank Mohsen Tondar, MD, Bahram Dehghan, MD, Alireza Pishva, MD, Koorosh Hashemi-Asl, MD, Zohreh Goudarznezhad, MA, Ali Asghar Nasihatkon, MSc, Iman Hafizi-Rastani, MSc, Mozhgan Tabatabaie, BSc, Mohsen Ebrahimi, MSc, Maryam Akhlaghinasab, MScN, and Mahvash Pourhassan, BScN, from Petroleum Industry Health Organization centers for providing the relevant data; none of them received any compensation.

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