Table 1

Characteristics of included studies of vaccines given before infection

Study, year, countryStudy type and timeframePatient or data sourceIntervention populationInterventionComparatorOutcomes of interest and length of follow-up
Al-Aly 2022,
USA19		Retrospectively assembled cohort.
1 January-1 December 2021		US Veterans Health Administration electronic health databasesn=33 940 patients who were fully vaccinated ≥14 days before a positive covid-19 test result, who were still alive 30 days after a positive test resultOne dose of Janssen, or two doses of Moderna or Pfizern=113 474 propensity score matched patients who were not vaccinated and alive 30 days after a positive covid-19 test result and no vaccinationRisk of ≥1 sequelae after the acute infection at 6 months
Antonelli 2022,
UK20		Prospective, community based, nested, case-control study, 8 December 2020-4 July 2021Covid-19 symptom study app usersn=3071 adult app users with a positive covid-19 test result ≥14 days after their first vaccine or at least seven days after their second vaccine; had no positive test result before vaccination and who had used the app for ≥14 consecutive days after the testFirst or second dose of Pfizer, Moderna, or AstraZenecan=3244 participants reporting a positive SARS-CoV-2 test result who were not vaccinated and who had used the app for ≥14 days after the testLong duration (≥1 month) of symptoms after one dose. Most common symptoms
Ayoubkhani 2022, UK, preprint21Retrospectively assembled cohort, 26 April 2020-30 November 2021Covid-19 infection survey participantsn=3090 adult participants who tested positive for SARS-CoV-2 between 26 April 2020 and 30 November 2021; who had received two vaccines at least two weeks before infectionTwo or more doses of AstraZeneca, Pfizer, or Modernan=3090 1:1 propensity score matched patients based on sociodemographic characteristics and time from infection to follow-up for long covid who were not vaccinatedRates of long covid >3 months after infection
Azzolini 2022, Italy22Retrospective cohort, March 2020-April 2022Healthcare workers from nine hospitalsn=318 healthcare workers who received >1 dose of vaccine before SARS-CoV-2 infectionOne, two, or three doses of Pfizern=421 healthcare workers who were not vaccinated before infectionRates of long covid >1 month after infection
Ioannou 2022,
USA23		Retrospectively assembled cohort.
1 Feb 2020-30 Apr 2021		US Veterans Health Administration electronic health databasesn=8357 people with 1-2 doses of vaccines with a positive SARS-CoV-2 test result between 1 February 2020 and 30 April 2021, who were still alive 3 months after infection, with no evidence of reinfectionOne or two doses of Moderna or Pfizern=58 693 people who were not vaccinated at the time of infection, who were still alive three months after infection, with no evidence of reinfectionRates and risk factors of long covid. Care at >3 months after infection
Mohr 2022,
USA, preprint24		Prospective cohort, December 2020-August 2021Healthcare professionals in 12 states participating in vaccine effectiveness study (PREVENT trial)n=180 healthcare professionals who had two doses of vaccines >14 days before covid-19 diseaseTwo doses of Moderna or Pfizern=239 healthcare professionals who had covid-19 with no previous vaccinationPresence of symptoms 1.5 months after onset of covid-19 disease
Pell 2022, UK,
preprint25		Prospective cohort, April 2020-May 2021Long Covid in Scotland Study (Long CISS)n=1154 adults with 1-4 doses of vaccine, who had a positive PCR test resultNot specifiedn=32 127 adults who were not vaccinatedConfusion and difficulty concentrating at 6-18 months
Simon 2021,
USA, preprint31		Retrospectively assembled cohort, February 2020-May 2021Arcadia data research dataset with >150 million patient recordsn=2392 patients who had their first dose of vaccine before a diagnosis of covid-19One dose of Pfizer, Moderna, or Janssenn=220 460 patients who were not vaccinated before covid-19 and 12 weeks afterOdds of having long covid at 3 months
Tannous 2022,
USA, preprint26		Retrospectively assembled cohort, 3 March 2020-20 November 2021Houston Methodist Covid-19 Surveillance and Outcomes Registry (CURATOR) electronic health record databasen=3781 adult patients vaccinated >14 days before covid-19 diseaseTwo doses of mRNA vaccines or one dose of Janssenn=49 458 patients who were not vaccinatedOdds of having long covid >1 month. Most common symptoms
Taquet 2021,
USA27		Retrospectively assembled cohort, 1 Janurary-31 August
2021		TriNetX Analytics, a federated network of linked electronic health records, with 81 million patient recordsn=9479 adults who received a covid-19 vaccine at least 2 weeks before SARS-CoV-2 infectionPfizer, Moderna, or
Janssen		n=9479 propensity matched patients who had received the influenza vaccine at any timeOdds of having any long covid symptoms within 6 months
van der Maaden,
Netherlands, preprint28		Prospective cohort, 19 May-13 December 2021Dutch prospective long covid studyn=3838 adult patients (aged <65), who were fully vaccinated three months after a positive SARS-CoV-2 test result>1 dose of Janssen or >2 doses of mRNA vaccinen=528 patients (<65 years) who were not vaccinated, three months after a positive SARS-CoV-2 test resultOdds of at least one significantly raised long covid symptom at >2 months
Zisis 2022,
USA29		Retrospectively assembled cohort, 21 September 2020-14 December 2021TriNetX Analytics, a federated network of linked electronic health records, with 81 million patient recordsn=25 225 adult patients who were vaccinated with a confirmed diagnosis of covid-19Not specifiedn=25225 1:1 propensity score matched patients who were not vaccinatedNew onset of long covid symptoms such as fatigue at 3 month follow-up

  • PCR=polymerase chain reaction; PREVENT=Project PREVENT (PReventing Emerging Infections through Vaccine EffectiveNess Testing Project) trial.