An interesting research article published by Bertollini and others in the Journal of the American Medical Association dated June 9, 2021 provides the answers to this.
The SARS-CoV-2 pandemic has severely affected international travel. Qatar implemented a pilot programme between February 18 and April 26, 2021 to ease travel restrictions by waiving the quarantine requirement for vaccinated residents who had received their second vaccine dose at least 14 days before arrival. The programme still required a PCR test to be performed on each passenger upon arrival at Hammad International Airport. This paper researched the incidence of PCR positive test results in arriving passengers.
The researchers assessed whether vaccination with either the Pfizer or Moderna vaccine and prior infection were associated with a lower risk for testing PCR positive.
PCR positivity in vaccinated persons and those with a documented prior infection were compared with PCR positivity in those with no record of vaccination or no record of prior infection. They were age, sex, nationality and testing date to control for differences in exposure rate and SARS-CoV-2 variant exposure analysed.
Fully vaccinated was defined as at least 14 days after the second dose before the airport PCR test.
Reinfection was defined as the first PCR positive swab at least 90 days after a prior infection.
Individuals with a PCR positive swab test less than 90 days before the airport test and vaccinated persons who had received only one dose or who did not present at least 14 days after the second dose were excluded from the study.
Results:
In total 261849 persons, 75.1% male were tested using PCR upon arrival at the Qatar Airport. The median age was 33 years.
Of the 31190 completely vaccinated individuals and of the 215901 individuals with no record of vaccination or prior infection, 10092 individuals could be matched, amongst whom PCR positivity was 0.82% and 3.74% respectively.
Of the 9180 individuals with no record of vaccination, but a record of prior infection at least 90 days before the PCR test, 7694 could be matched to individuals with no record of vaccination or prior infection and amongst this group PCR positivity was 1.01% compared with 3.81% respectively.
The relative risk for PCR positivity was 0.22 for vaccinated individuals and 0.26 for individuals with prior infection compared with no record of vaccination or prior infection.
Sequencing of the 72 PCR positive specimens from arriving passengers identified the beta variant to be 44.4%, the alpha variant to be 27.8% and the delta variant to be 11% and wild type strain of 16.7%.
Discussion:
Vaccination and prior infection were associated with a reduced risk for SARS-CoV-2 PCR test positivity in residents of Qatar returning on international flights. Nevertheless, both vaccine immunity and natural immunity were not perfect, with breakthrough infections recorded. This highlights the need to maintain PCR testing for arriving travellers.
The London General Practice, the leading London Doctor’s clinic, commends the Government on its vaccination programme and encourages all those eligible to be vaccinated.
LGP, the leading London Doctor’s clinic, provides all forms of travel COVID testing including fit to fly, test for release day five and day two and day eight testing. These can be booked online.
Dr Paul Ettlinger
Founder, The London General Practice