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Cited by 1,345SARS-CoV-2 and COVID-19 ResearchCOVID-19 Clinical Research StudiesCOVID-19 epidemiological studies

Covid-19 Breakthrough Infections in Vaccinated Health Care Workers

Open access
Bergwerk, Moriah, Gonen, Tal, Lustig, Yaniv, Amit, Sharon, Lipsitch, Marc, Cohen, Carmit, Mandelboim, Michal, Levin, Einav Gal +8 more·2021·New England Journal of Medicine
DOI 10.1056/nejmoa2109072PMC PMC8362591
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Abstract

BACKGROUND: Despite the high efficacy of the BNT162b2 messenger RNA vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), rare breakthrough infections have been reported, including infections among health care workers. Data are needed to characterize these infections and define correlates of breakthrough and infectivity. METHODS: At the largest medical center in Israel, we identified breakthrough infections by performing extensive evaluations of health care workers who were symptomatic (including mild symptoms) or had known infection exposure. These evaluations included epidemiologic investigations, repeat reverse-transcriptase-polymerase-chain-reaction (RT-PCR) assays, antigen-detecting rapid diagnostic testing (Ag-RDT), serologic assays, and genomic sequencing. Correlates of breakthrough infection were assessed in a case-control analysis. We matched patients with breakthrough infection who had antibody titers obtained within a week before SARS-CoV-2 detection (peri-infection period) with four to five uninfected controls and used generalized estimating equations to predict the geometric mean titers among cases and controls and the ratio between the titers in the two groups. We also assessed the correlation between neutralizing antibody titers and N gene cycle threshold (Ct) values with respect to infectivity. RESULTS: Among 1497 fully vaccinated health care workers for whom RT-PCR data were available, 39 SARS-CoV-2 breakthrough infections were documented. Neutralizing antibody titers in case patients during the peri-infection period were lower than those in matched uninfected controls (case-to-control ratio, 0.361; 95% confidence interval, 0.165 to 0.787). Higher peri-infection neutralizing antibody titers were associated with lower infectivity (higher Ct values). Most breakthrough cases were mild or asymptomatic, although 19% had persistent symptoms (>6 weeks). The B.1.1.7 (alpha) variant was found in 85% of samples tested. A total of 74% of case patients had a high viral load (Ct value, <30) at some point during their infection; however, of these patients, only 17 (59%) had a positive result on concurrent Ag-RDT. No secondary infections were documented. CONCLUSIONS: Among fully vaccinated health care workers, the occurrence of breakthrough infections with SARS-CoV-2 was correlated with neutralizing antibody titers during the peri-infection period. Most breakthrough infections were mild or asymptomatic, although persistent symptoms did occur.

Integrity signals

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Crossref · 10.1056/nejmoa2109072

Cites

Statistics

Nothing to recompute.

Claims the paper makes

0 of 27 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    No secondary infections were detected among household contacts of 31 cases, including 10 case patients and their 27 household members.

    “Among the 31 cases for whom data regarding household transmission (including symptoms and RT-PCR results) were available, no secondary infections were detected, including 10 case patients and their 27 household members in whom the health care worker was the only index case patient.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The contact tracing for in-hospital and household contacts was complete enough to detect any secondary infections.
  • Findingown data

    Most breakthrough infections among the health care workers were mild or asymptomatic.

    “Most breakthrough cases were mild or asymptomatic, although 19% had persistent symptoms (>6 weeks).”
    • Also stated in: § Breakthrough Infections · plain
      “Of all the workers with breakthrough infection, 26 (67%) had mild symptoms at some stage, and none required hospitalization. The remaining 13 workers (33% of all cases) were asymptomatic during the duration of infection; of these workers, 6 were defined as borderline cases, since they had an N gene Ct value of more than 35 on repeat testing.”
    Quote in the paperNot a substantial claim
  • Findingown data

    The breakthrough infection rate among fully vaccinated health care workers was 0.4%.

    “We found a low rate of breakthrough infection (0.4%).”
    Quote in the paperSubstantial claim
  • Findingown data

    Peri-infection S-specific IgG antibody levels were lower in breakthrough cases than in controls (predicted ratio, 0.514; 95% CI, 0.282 to 0.937).

    “The observed and predicted GMTs of peri-infection S-specific IgG antibody levels in breakthrough infection cases were lower than that in controls, with a predicted ratio of 0.514 (95% CI, 0.282 to 0.937) (Figure 2C).”
    Quote in the paperSubstantial claim
  • Findingown data

    74% of breakthrough case patients had a high viral load (Ct value <30) at some point during infection.

    “A total of 74% of case patients had a high viral load (Ct value, <30) at some point during their infection; however, of these patients, only 17 (59%) had a positive result on concurrent Ag-RDT.”
    • Also stated in: § Verification Testing and Secondary Infections · plain
      “A total of 29 case patients (74%) had a Ct value of less than 30 at some point during their infection.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. 9
  • May combine two claims. 17
  • The quote only partly states this claim. 1

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    13.1% of fully vaccinated health care workers underwent RT-PCR testing during the study period.

    “Among 11,453 fully vaccinated health care workers, 1497 (13.1%) underwent RT-PCR testing during the study period.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Postinfection N-specific IgG antibodies were assessed in 22 of 39 case patients (56%) on days 8 to 72 after first positive RT-PCR; 4 (18%) had no immune response.

    “Data regarding postinfection N-specific IgG antibodies were available for 22 of 39 case patients (56%) on days 8 to 72 after the first positive result on RT-PCR assay. Of these workers, 4 (18%) did not have an immune response, as detected by negative results on N-specific IgG antibody testing.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In all 37 case patients with source data, the suspected source of infection was an unvaccinated person; in 21 (57%) it was a household member.

    “In all 37 case patients for whom data were available regarding the source of infection, the suspected source was an unvaccinated person; in 21 patients (57%), this person was a household member.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In 11 of 37 case patients (30%), the suspected source was an unvaccinated fellow health care worker or patient; 7 of these 11 were linked to a nosocomial outbreak of the B.1.1.7 variant.

    “In 11 of 37 case patients (30%), the suspected source was an unvaccinated fellow health care worker or patient; in 7 of the 11 case patients, the infection was caused by a nosocomial outbreak of the B.1.1.7 (alpha) variant.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The cohort included health care workers who were mostly young and healthy, and all breakthrough cases were mild.

    “Furthermore, our cohort included health care workers who were mostly young and healthy, and all breakthrough cases were mild.”
    Quote in the paperNot a substantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    Peri-infection neutralizing antibody test results were available for 22 breakthrough cases, and the case-control analysis included these 22 cases and 104 matched controls.

    “The results of peri-infection neutralizing antibody tests were available for 22 breakthrough cases.”
    • Also stated in: § Case–Control Analysis · plain
      “In total, 22 breakthrough cases and their 104 matched controls were included in the case–control analysis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    26% of breakthrough case patients had an N gene Ct value >30 throughout infection, and 6 of these had values >35.

    “Ten workers (26%) had an N gene Ct value of more than 30 throughout the entire period; 6 of these workers had values of more than 35 and probably had never been infectious.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The test positivity in the study was 2.6%, with more than 38 persons tested per positive case.

    “More than 38 persons were tested for every positive case that was detected, for a test positivity of 2.6%.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The breakthrough cases were less contagious than unvaccinated persons, as supported by no secondary infections and previous reports.

    “However, no secondary infections were traced back to any of the breakthrough cases, which supports the inference that these workers were less contagious than unvaccinated persons, as has been reported previously.4,5,17,18”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [4] Regev-Yochay G, Amit S, Bergwerk M, et al. Decreased infectivity following BNT162b2 vaccination: a prospective cohort study in Israel. Lancet Reg Health Eur 2021; 7: 100150- 100150. 34250518 PMC8261633 source

      Not checked in the free run.

    • cites [5] Petter E, Mor O, Zuckerman N, et al. Initial real world evidence for lower viral load of individuals who have been vaccinated by BNT162b2. February 8, 2021 (https://www.medrxiv.org/content/10.1101/2021.02.08.21251329v1). preprint. source

      Not checked in the free run.

    • cites [17] Pratò S, Paladino ME, Riva MA, Deni M, Belingheri M. SARS-CoV-2 transmission risk to household and family contacts by vaccinated healthcare workers. J Occup Environ Med 2021; 63(7): e474- e476. 34184663 PMC8247537 source

      Not checked in the free run.

    • cites [18] Shah ASV, Gribben C, Bishop J, et al. Effect of vaccination on transmission of COVID-19: an observational study in healthcare workers and their households. March 21, 2021 (https://www.medrxiv.org/content/10.1101/2021.03.11.21253275v1). preprint.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • Rests on an assumption: The contact tracing for in-hospital and household contacts was complete enough to detect any secondary infections.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    At the time of the study, B.1.1.7 was the most widespread variant in Israel and accounted for up to 94.5% of SARS-CoV-2 isolates.

    “At the time of this study, the B.1.1.7 variant was the most widespread variant in Israel and accounted for up to 94.5% of SARS-CoV-2 isolates.1,16”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [1] Haas EJ, Angulo FJ, McLaughlin JM, et al. Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data. Lancet 2021; 397: 1819- 1829. 33964222 PMC8099315 source

      Not checked in the free run.

    • cites [16] Kustin T, Harel N, Finkel U, et al. Evidence for increased breakthrough rates of SARS-CoV-2 variants of concern in BNT162b2-mRNA-vaccinated individuals. Nat Med 2021 June 14 (Epub ahead of print). 34127854 PMC8363499 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Repeat RT-PCR assays were performed for all case patients with initial N gene Ct >30 to verify that the initial test was not taken too early.

    “Repeat RT-PCR assays were performed on samples obtained from most of the infected workers and for all case patients with an initial N gene Ct value of more than 30 to verify that the initial test was not taken too early, before the worker had become infectious.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Reports have been published in which certain variants of concern were more prevalent in breakthrough infections.

    “In contrast, reports in which certain variants of concern were more prevalent in breakthrough infections have been published as well.8,16,26”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [8] Hacisuleyman E, Hale C, Saito Y, et al. Vaccine breakthrough infections with SARS-CoV-2 variants. N Engl J Med 2021; 384: 2212- 2218. 33882219 PMC8117968 source

      Not checked in the free run.

    • cites [16] Kustin T, Harel N, Finkel U, et al. Evidence for increased breakthrough rates of SARS-CoV-2 variants of concern in BNT162b2-mRNA-vaccinated individuals. Nat Med 2021 June 14 (Epub ahead of print). 34127854 PMC8363499 source

      Not checked in the free run.

    • cites [26] Philomina J B, Jolly B, John N, et al. Genomic survey of SARS-CoV-2 vaccine breakthrough infections in healthcare workers from Kerala, India. J Infect 2021 May 25 (Epub ahead of print). 34044037 PMC8143909 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Vaccine-induced immunity is greatly protective against clinical disease but somewhat less protective against infection and infectivity.

    “This result may eventually be even more important, since vaccine-induced immunity has been shown to be greatly protective against clinical disease but somewhat less protective against both infection and infectivity.4”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4] Regev-Yochay G, Amit S, Bergwerk M, et al. Decreased infectivity following BNT162b2 vaccination: a prospective cohort study in Israel. Lancet Reg Health Eur 2021; 7: 100150- 100150. 34250518 PMC8261633 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductown data

    The study matched each breakthrough case with four or five uninfected controls on sex, age, interval between second vaccine dose and serologic testing, and immunosuppression status.

    “For each breakthrough case, we matched samples that had been obtained from four or five uninfected controls according to the following variables: sex, age, the interval between the second dose of BNT162b2 vaccine and serologic testing, and immunosuppression status.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    A case-control ratio of 1:4 or 1:5 was selected to maximize statistical power.

    “A case–control ratio of 1:4 or 1:5 was selected to maximize the statistical power of the study.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The study performed a sensitivity analysis with a different order of covariates in the matching algorithm to confirm robustness.

    “To further confirm the robustness of our matching criteria, we performed a sensitivity analysis with a different order of covariates in the matching algorithm that used a uniform age criterion and did not match for sex.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    In 13 case patients with both values, peri-infection antibody titers were lower than previous peak titers, indicating that day-of-diagnosis titers were probably representative of peri-infection titers.

    “In all cases, peri-infection titers were lower than the previous peak titers, indicating that the titers that were obtained on the day of diagnosis were probably representative of peri-infection titers (Fig. S2).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    At least in some cases, the vaccine protected against symptomatic disease but not against infection.

    “This factor suggests that at least in some cases, the vaccine protected against symptomatic disease but not against infection.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The finding that peak titer differences were more strongly associated with risk is consistent with the hypothesis that postvaccination neutralizing antibody titer is a marker of overall immune response and suggests a possible role for IgG titer.

    “This finding was consistent with the hypothesis that the neutralizing antibody titer after vaccination is a marker of overall immune response and suggested a possible role for the IgG titer.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The BNT162b2 vaccine reduces the incidence of asymptomatic infection and associated infectivity.

    “The vaccine has also been shown to reduce the incidence of asymptomatic infection and the associated infectivity.4,5”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [4] Regev-Yochay G, Amit S, Bergwerk M, et al. Decreased infectivity following BNT162b2 vaccination: a prospective cohort study in Israel. Lancet Reg Health Eur 2021; 7: 100150- 100150. 34250518 PMC8261633 source

      Not checked in the free run.

    • cites [5] Petter E, Mor O, Zuckerman N, et al. Initial real world evidence for lower viral load of individuals who have been vaccinated by BNT162b2. February 8, 2021 (https://www.medrxiv.org/content/10.1101/2021.02.08.21251329v1). preprint. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    95% of vaccinated health care workers had a neutralizing antibody titer >256 within 2 weeks after the second BNT162b2 dose.

    “We have previously reported that 95% of vaccinated health care workers were found to have a neutralizing antibody titer of more than 256 within 2 weeks after the second BNT162b2 vaccine dose.11”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [11] Lustig Y, Sapir E, Regev-Yochay G, et al. BNT162b2 vaccine-induced immune responses and dynamics vary among age groups, sex and co-morbidities: a longitudinal prospective cohort study. March 4, 2021 (https://ssrn.com/abstract=3790408). preprint. source

      Not checked in the free run.

  • May combine two claims.

    Study design and conductown data

    The cohort represented mostly young and healthy persons, and all breakthrough infections were mild and did not require hospitalization; therefore the study could not determine the correlate of protection from severe infection or infection in vulnerable older persons with coexisting illnesses.

    “Second, this cohort represents mostly young and healthy persons, and all breakthrough infections were mild and did not require hospitalization. Thus, we could not determine the correlate of protection from severe infection or infection in vulnerable populations of older persons with coexisting illnesses.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Rare breakthrough infections carry an infectious potential and create a special challenge because they are often asymptomatic and may pose a risk to vulnerable populations.

    “In this study, we found that although the BNT162b2 vaccine is extremely effective, rare breakthrough infections carry an infectious potential and create a special challenge, since such infections are often asymptomatic and may pose a risk to vulnerable populations.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    Controls were not matched according to testing or exposure, only according to timing of serologic testing in vaccinated, uninfected health care workers; therefore the study could not control for differences in exposure risk.

    “Fourth, the controls were not matched according to testing or exposure but only according to the timing of serologic testing in vaccinated, uninfected health care workers. Thus, we could not control for differences in the risk of exposure to Covid-19.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The study was not designed to address the question of variants of concern in breakthrough infections.

    “Our study was not designed to address this question regarding variants of concern in breakthrough infections.”
    Quote in the paperNot a substantial claim
25 of 25

  • The authors state this as an assumption.

    The presence of neutralizing antibodies correlates with protection from reinfection with SARS-CoV-2.

    “The assumption that the presence of neutralizing antibodies would correlate with protection from reinfection with SARS-CoV-2 has been supported by studies comparing the incidence of infection between seropositive and seronegative persons.9,19”

  • The paper relies on this without support.

    The contact tracing for in-hospital and household contacts was complete enough to detect any secondary infections.

    “Thorough epidemiologic investigations of data regarding in-hospital contact tracing did not detect any cases of transmission from infected health care workers (secondary infections) among the 39 primary infections.”
    “Among the 31 cases for whom data regarding household transmission (including symptoms and RT-PCR results) were available, no secondary infections were detected, including 10 case patients and their 27 household members in whom the health care worker was the only index case patient.”

  • The paper relies on this without support.

    The matched controls were uninfected at the time of antibody measurement.

    “We matched patients with breakthrough infection who had antibody titers obtained within a week before SARS-CoV-2 detection (peri-infection period) with four to five uninfected controls”
    “For each breakthrough case, we matched samples that had been obtained from four or five uninfected controls according to the following variables: sex, age, the interval between the second dose of BNT162b2 vaccine and serologic testing, and immunosuppression status.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Neutralizing antibodies can serve as a correlate of protection against SARS-CoV-2 infection.

    “A correlation between neutralizing antibody titers and infectivity was recently reported6 and suggested that although the specific threshold titer that can predict breakthrough infection is still undefined, neutralizing antibodies may be used as a correlate of protection.”

    From Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months (2021) · cites this paper as [6]

  • Neutralizing antibodies have been shown to correlate with protection against SARS-CoV-2.

    “Neutralizing antibodies have been shown to correlate with protection.6,15”

    From Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months (2021) · cites this paper as [6]

  • In previously reported work, breakthrough infection among BNT162b2-vaccinated people was correlated with neutralizing antibody titers.

    “We recently reported that breakthrough infection in BNT162b2-vaccinated persons was correlated with neutralizing antibody titers.6”

    From Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months (2021) · cites this paper as [6]

No citation lists for this paper

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References 25 · Cited by 1,345

Research works printed but not linked: 3

  1. Shah ASV Gribben C Bishop J et al. Effect of vaccination on transmission of COVID-19: an observational study in healthcare workers and their households. March 21 2021 (https://www.medrxiv.org/content/10.1101/2021.03.11.21253275v1). preprint. · DOI
  2. Jacobson KB Pinsky BA Rath MEM et al. Post-vaccination SARS-CoV-2 infections and incidence of the B.1.427/B.1.429 variant among healthcare personnel at a northern California academic medical center. April 24 2021 (https://www.medrxiv.org/content/10.1101/2021.04.14.21255431v2). preprint. · DOI · Paper page
  3. Bouton TC Lodi S Turcinovic J et al. COVID-19 vaccine impact on rates of SARS-CoV-2 cases and post vaccination strain sequences among healthcare workers at an urban academic medical center: a prospective cohort study. April 27 2021 (https://www.medrxiv.org/content/10.1101/2021.03.30.21254655v2). preprint. · DOI · Paper page

Authors
Bergwerk, M., Gonen, T., Lustig, Y., Amit, S., Lipsitch, M., Cohen, C., Mandelboim, M., Levin, E. G., Rubin, C., Indenbaum, V., Tal, I., Zavitan, M., Zuckerman, N., Bar-Chaim, A., Kreiss, Y., & Regev-Yochay, G.
Affiliations
  • Tel Aviv University (IL)
  • From the Infection Prevention and Control Unit (M.B., T.G., C.C., E.G.L., C.R., I.T., M.Z., G.R.-Y.), the Department of Clinical Microbiology (S.A.), General Management (Y.K.), and the Central Virology Laboratory, Public Health Authority, Ministry of Health (Y.L., M.M., V.I., N.Z.), Sheba Medical Center Tel Hashomer, Ramat Gan, Sackler School of Medicine, Tel Aviv University, Tel Aviv (T.G., Y.L., M.M., E.G.L., Y.K., G.R.-Y.), and the Laboratory Wing, Asaf Harofe Medical Center, Be’er Ya’akov (A.B.-C.) — all in Israel; St. George’s School of Medicine of London and Faculty of Medicine, University of Nicosia, Nicosia, Cyprus (M.B.); and Harvard T.H. Chan School of Public Health, Boston (M.L.).
ORCID
Venue
New England Journal of Medicine
Publisher
Massachusetts Medical Society
Published
2021-10-14
Volume
385
Issue
16
Pages
1474-1484
ISSN
  • 0028-4793 (ISSN-L)
  • 1533-4406
DOI
10.1056/nejmoa2109072
PMC
PMC8362591
OpenAlex
W3184172540
Cited by
1,345
References
25
Citations by year
2026: 21 · 2025: 55 · 2024: 138 · 2023: 262 · 2022: 641 · 2021: 226 · 2020: 1
FWCI
101.19
Type
journal article
Language
en
Open access
Locations
  • New England Journal of Medicine (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • ImmPort
Funders
National Cancer Institute (U01CA261277)
Topics
  • Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
  • Health Sciences › Medicine › Infectious Diseases › COVID-19 Clinical Research Studies
  • Physical Sciences › Mathematics › Modeling and Simulation › COVID-19 epidemiological studies
Keywords
COVID-19 pandemic, SARS-CoV-2, breakthrough infection, BNT162b2 mRNA vaccine, healthcare workers, neutralizing antibody titer, vaccine efficacy, viral load, B.1.1.7 variant, asymptomatic infection, persistent symptoms, infectivity, antibody waning
MeSH terms
COVID-19, COVID-19 Vaccines, COVID-19 Nucleic Acid Testing, BNT162 Vaccine, Breakthrough Infections, Adult, Female, Health Personnel, Humans, Israel, Male, Middle Aged, Case-Control Studies, Treatment Failure, Reverse Transcriptase Polymerase Chain Reaction, Asymptomatic Diseases

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