The idea now is that the document has a life span of nine months after the first set of vaccines are administered — so after the second dose for Pfizer-BioNTech shot, for example, or after one dose of the Johnson & Johnson vaccine. The idea is that as immunity wanes, then a vaccine passport will expire.

Thursday’s recommendation does not yet address booster shots. The commission said that “it can reasonably be expected that protection from booster vaccinations may last longer than that resulting from the primary vaccination series.”

As such, a new expiration date could be announced in a couple of week’s time to include the advice for booster shots. In a major policy shift, the European Centre for Disease Prevention and Control suggested Wednesday that all adults should receive vaccine boosters, with priority given to those over 40.