Well, if the large majority of your population is already vaccinated, I guess these passports could potentially be dismissed, if masks are still mandatory, but for some countries - like Portugal where we have +80% of the pop. vaccinated - the main concern are tourists that completely disregard any etiquette or measures in place. So I think keeping passports is a good measure, not perfect due to breakthrough infection…
Last time I checked, the top 3 countries in terms of vaccination rates are also the top 3 countries in terms of number of active covid cases. Israel is #1 in vaccination rates and #1 in daily cases.
Last week Portugal was number 2, and our cases have been dropping (which is a good sign for winter, though it's still early), also deaths and hospitalizations are nowhere near pre-vaccine numbers.
We even had breakthrough cases in homes and care centers for the elderly, the majority seem to be mildly symptomatic or asymptomatic, very few deaths.