Israel and Bahrain want eligible residents to take their Covid booster shots — and those who don’t do so risk losing their fully-vaccinated status, and the privileges that come with it.

In Israel, vaccinated people are given a so-called “green pass” that allows them to enter hotels, restaurants and many other indoor venues.

People who have recovered from Covid-19 can also be issued a green pass under a different set of guidelines.

As of Oct. 3, Israel shortened the validity of the green pass. According to a government advisory, the pass will expire six months after a person receives their second dose.

A third shot will have to be administered before a new green pass can be issued, at least one week after the booster. That pass will also expire six months after the third dose. It is unclear whether more boosters may be needed in future to be considered fully vaccinated.

Protests broke out in Israel over the new policy, and an estimated 2 million could lose their Green Pass, Associated Press reported.

Bahrain has taken a similar approach.

People who are eligible for their booster shots will see their vaccination status lowered on the kingdom’s digital vaccine passport, the BeAware mobile application. A lower status restricts a person’s public movements and activities.

Previously, those with a green shield were considered fully vaccinated two weeks after the second dose. However, under new regulations, the vaccination status of individuals eligible for a booster will be changed on the app “from the Green Shield to the Yellow Shield until they opt to receive a booster shot.”

It is unclear if the same policy will apply for future doses that may be required.

Based on current restrictions in Bahrain, only those who have recovered from Covid, are under 12 years old or have green shields can go to the movie theaters, organize indoor events and conferences, or attend indoor sporting events.

Health experts are broadly divided on the need for booster programs. Most agree that the efficacy of vaccines will wane over time, but experts disagree over whether booster shots are needed for everyone.

“Current evidence does not, therefore, appear to show a need for boosting in the general population, in which efficacy against severe disease remains high,” a group of leading scientists said in September. The wide distribution of boosters is “not appropriate at this stage in the pandemic,” they added.

The WHO also objects to third shots, describing it as “not right” when people in other countries have yet to receive their first and second doses. The UN health agency this week recommended booster shots for people who are moderately or severely immunocompromised.

The U.S. has already approved booster shots for some people who took the Pfizer-BioNTech vaccine six months ago. They include those who are 65 years and older, adults with underlying medical conditions and people in high-risk occupational and institutional settings.

After initial speedy vaccination campaigns, Israel and Bahrain rolled out booster doses to large swathes of their populations.

Their approach is more aggressive than most other countries, which have mostly focused on third doses for seniors and other vulnerable groups.

In Israel, which mostly relied on Pfizer–BioNTech Covid vaccines, the booster program has been expanded to everyone 12 years and older.

Israel’s data appeared to show that the two-dose vaccine was just 39% effective between June 20 and July 17, but a third dose would restore protection from infection to 95%, Pfizer said in September.

Bahrain has different criteria for each of the vaccines offered. However, most people 18 years and above will be eligible for a booster shot six months after the second dose.

Data in the kingdom found that from July 1 to Oct. 1, 52% of those who were infected did not take a booster dose. By comparison, 3% of confirmed cases were in people who received a third dose.

“It is therefore clear that booster shots increase immunity,” a government news release said.

— CNBC’s Berkeley Lovelace Jr., Rich Mendez, Natasha Turak and Robert Towey contributed to this report.