Tourists arrive at Palma de Mallorca, Spain, last summer. The EU’s executive arm has proposed a certificate to ease travel across its member states.

Tourists arrive at Son Sant Joan airport in Palma de Mallorca on June 22, 2020 as EU member state citizens and those from the passport-free Schengen zone were allowed freely into Spain, with no 14-day quarantines required following a national lockdown to stop the spread of the novel coronavirus. (Photo by JAIME REINA / AFP) (Photo by JAIME REINA/AFP via Getty Images)