LJUBLJANA, Slovenia (AP) — Slovenia suspended use of the Johnson & Johnson coronavirus vaccine Wednesday while it investigates the death of a 20-year-old woman, as thousands started gathering for an anti-vaccination protest in the small European Union nation.

The suspension will be in place until experts determine whether there was a link between the woman's death from a stroke this week and the vaccine shot she received two weeks earlier, Health Minister Janez Poklukar said.

However, the vaccine’s “benefits continue to outweigh the risks” at this point, Poklukar said.

The one-dose J&J vaccine became more popular after Slovenian authorities introduced new requirements for COVID-19 passes, including for going to work in all state-run firms. The government approved the purchase of an additional 100,000 doses from Hungary in response to the growing demand.

The woman who died was the second recipient of the Johnson & Johnson vaccine in Slovenia to have experienced a serious health condition that wasn't COVID-19, the official STA news agency reported. About 120,000 people in Slovenia have received the vaccine.

The suspension announcement is likely to fuel the protests in the capital, Ljubljana, against vaccination and pandemic requirements.

Similar protests drew thousands previously, and demonstrators recently clashed with police. Ahead of Wednesday's event, police put up metal fences and urged participants to remain calm.

Like much of Central and Eastern Europe, Slovenia in recent weeks has seen a rise in infections. The country of some 2 million people has fully vaccinated nearly 48% of the population, a smaller share than in many other European Union member nations.

Slovenia has recommended Johnson & Johnson vaccines to all people over age 18, while some countries who have limited its use to older people.