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Volume 27, Number 4—April 2021

Postvaccination COVID-19 among Healthcare Workers, Israel

Sharon AmitComments to Author , Sharon Alexsandra Beni, Asaf Biber, Amir Grinberg, Eyal Leshem1, and Gili Regev-Yochay1
Author affiliation: Authors affiliation: Chaim Sheba Medical Center, Ramat-Gan, Israel

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Coronavirus disease (COVID-19) symptoms can be mistaken for vaccine-related side effects during initial days after immunization. Among 4,081 vaccinated healthcare workers in Israel, 22 (0.54%) developed COVID-19 from 1–10 days (median 3.5 days) after immunization. Clinicians should not dismiss postvaccination symptoms as vaccine-related and should promptly test for COVID-19.

Large-scale vaccination of risk groups and later the general population is the single most effective public health measure for mitigation of the coronavirus disease (COVID-19) pandemic. National COVID-19 vaccination programs started during December 2020 in several countries and prioritized healthcare workers (HCWs) (1). In some countries the vaccination programs coincided with a surge in detected COVID-19 cases and increased burden on the healthcare system (2).

During December 2020–January 2021, Israel experienced a surge in COVID-19 incidence that resulted in the third national lockdown imposed since the pandemic began in early 2020 (3). Concomitantly, during December 2020, Israel’s Ministry of Health approved the Pfizer-BioNTech COVID-19 vaccine (BNT162b2; Pfizer Inc., and prioritized HCWs for immunization (4).

Sheba Medical Center is a large hospital with 9,069 staff members in Ramat-Gan, Israel. The hospital started its personnel vaccination program on December 20, 2020, and excluded workers who had recovered from COVID-19. During the first week of the campaign, 4,081 (45%) eligible staff members received the first dose of BNT162b2. Concurrently, the national COVID-19 positivity rate rapidly increased to >6% on January 3, 2021 (2).

The Study

The hospital’s Infection Prevention and Control Unit conducted active and passive surveillance of vaccinated staff by using daily health questionnaires, hotlines, on-call infectious disease unit staff, and post-vaccination web-based questionnaires to identify and test symptomatic HCWs. Among 4,081 HCWs vaccinated in the first week of the campaign, 22 (0.54%) later had laboratory-confirmed COVID-19 (Table). The average age among COVID-19–positive vaccinated HCWs was 45.3 years (±9.85 years), and they belonged to different healthcare sectors and worked on various wards.

Among the 22 vaccinated HCWs who tested positive for COVID-19, 13 were tested because they had symptoms, most commonly an influenza-like illness that included fever, chills, cough, headache, myalgia, and sore throat. Two vaccinated HCWs were tested because of exposure to confirmed or suspected COVID-19 cases and because they reported symptoms upon questioning. Asymptomatic COVID-19 cases were identified among HCWs as part of postexposure screening. Among the 22 COVID-19–positive HCWs, 11 had presumable community-related exposures, 4 of whom reported exposure incidents that occurred before or on the date of vaccination. An investigation conducted by the hospital’s Infection Control and Prevention Unit identified 10 healthcare-related secondary exposures. However, we did not identify any point-source exposures or COVID-19 clusters linked to the immunization process.

Among the 11 vaccinated HCWs who reported COVID-19 symptoms, the median time between the first dose of BNT162b2 immunization and symptom onset was 3.5 (range 0–10) days; we excluded 1 vaccinee from our calculation and analysis because the HCW had symptoms before immunization (Table). The median time between the onset of symptoms and testing was 1 day, demonstrating the high level of suspicion for COVID-19 during the vaccination campaign.

Of note, apart from the need for early detection, persons who test positive for COVID-19 after receiving the first vaccine dose (whether asymptomatic and tested following exposure or tested because they are symptomatic) are not eligible to receive the second dose, according to Ministry of Health policy. However, depending on availability of vaccines, this policy might change when further data are collected.


COVID-19 in HCWs is a major concern for health authorities worldwide. HCWs, especially acute and chronic care facility personnel, are at high risk for contracting symptomatic and asymptomatic COVID-19 and might become infected at home or nosocomially while caring for patients or interacting with other staff members (57). Infections among HCWs have an immediate effect on their close occupational environment and the overall healthcare system. Secondary exposures, isolation, and infections of staff can substantially impair the capacity of a single ward to care for patients, creating a snowball effect with collateral damage to both the functional resilience of the facility and morale of staff. Consequently, as soon as COVID-19 vaccines were deployed in Israel, HCWs were the first group to receive it.

We report 22 cases of early, postimmunization, laboratory-confirmed COVID-19 among HCWs during the launch of the vaccination campaign in a large hospital in Israel. BNT162b2 is not likely to exert protection against clinical disease during the first days after receipt of the first dose. Efficacy of the BNT162b was 52% a week after the first dose, and positive COVID-19 cases were described among vaccinees even early after the second dose (8). Thus, during a large-scale immunization campaign coinciding with rapid national increase in COVID-19 cases, some immunized persons likely will develop clinical disease.

The co-occurrence of vaccination deployment with the rapidly climbing COVID-19 spread in many parts of the world is a confusing period in which hope is mixed with great vulnerability. The phenomenon of pandemic fatigue, in which the population tires of constant safety precautions, testing, isolation, and restrictions, could lead to less social distancing and personal protection. Pandemic fatigue coupled with the availability of a vaccine, might give the population a false sense of reassurance and consequently lead to a brisk increase in COVID-19 cases. Thus, almost every physical complaint after vaccination poses a true diagnostic dilemma as to whether an adverse reaction or a new COVID-19 infection is the cause. Undetected COVID-19 cases among HCWs could be hazardous for patients and other staff.

Clinicians should have a high level of suspicion of reported symptoms and avoid dismissing complaints as vaccine-related until true infection is ruled out and vaccinees are tested. Active and passive surveillance schemes that enable rapid testing and initiation of infection control measures are essential in preventing possible diagnostic delays and secondary exposures. Therefore, healthcare-related indications for testing should not be altered until systematic and exhaustive data are gathered regarding vaccine effectiveness in healthcare settings.

Dr. Amit is a certified internist, infectious disease specialist, and clinical microbiologist, and is the director of the Clinical Microbiology Department at Sheba Medical Center, Israel. Her fields of research include clinical microbiology and communicable diseases epidemiology.



  1. Dooling  K, McClung  N, Chamberland  M, Marin  M, Wallace  M, Bell  BP, et al. The Advisory Committee on Immunization Practices’ interim recommendation for allocating initial supplies of COVID-19 vaccine—United States, 2020. MMWR Morb Mortal Wkly Rep. 2020;69:18579. DOIPubMedGoogle Scholar
  2. Johns Hopkins University Center for Systems Science and Engineering. COVID-19 dashboard. 2020 [cited 2021 Jan 3].
  3. Leshem  E, Afek  A, Kreiss  Y. Buying time with COVID-19 outbreak response, Israel. Emerg Infect Dis. 2020;26:22513. DOIPubMedGoogle Scholar
  4. State of Israel Ministry of Health. Coronavirus (COVID-19) vaccines [in Hebrew]. 2020 [cited 2021 Jan 3].
  5. Calcagno  A, Ghisetti  V, Emanuele  T, Trunfio  M, Faraoni  S, Boglione  L, et al. Risk for SARS-CoV-2 infection in healthcare workers, Turin, Italy. Emerg Infect Dis. 2021;27:3035. DOIPubMedGoogle Scholar
  6. Feaster  M, Goh  YY. High proportion of asymptomatic SARS-CoV-2 infections in 9 long-term care facilities, Pasadena, California, USA, April 2020. Emerg Infect Dis. 2020;26:24169. DOIPubMedGoogle Scholar
  7. Akinbami  LJ, Vuong  N, Petersen  LR, Sami  S, Patel  A, Lukacs  SL, et al. SARS-CoV-2 seroprevalence among healthcare, first response, and public safety personnel, Detroit metropolitan area, Michigan, USA, May–June 2020. Emerg Infect Dis. 2020;26:286371. DOIPubMedGoogle Scholar
  8. Polack  FP, Thomas  SJ, Kitchin  N, Absalon  J, Gurtman  A, Lockhart  S, et al.; C4591001 Clinical Trial Group. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med. 2020;383:260315. DOIPubMedGoogle Scholar




Cite This Article

DOI: 10.3201/eid2704.210016

Original Publication Date: February 01, 2021

1These authors equally contributed to the study.

Table of Contents – Volume 27, Number 4—April 2021

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Address for correspondence: Sharon Amit, Clinical Microbiology, The Chaim Sheba Medical Center, Ramat Gan, Israel

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Page created: January 25, 2021
Page updated: March 18, 2021
Page reviewed: March 18, 2021
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