Six fully vaccinated people who attended an outdoor wedding in Texas in April came down with Covid-19, a new study says — a small outbreak that underscores how effective US-authorized vaccines are against even variants of the virus.

Though the vaccines made by Pfizer and Moderna may not knock out every Covid-19 case, especially now that the more infectious Delta variant dominates across the U.S., they are very good at preventing death from Covid-19.

The preprint study from Baylor College of Medicine found that only one person who'd gotten an Indian-made vaccine, Covaxin, died after attending the 92-person wedding near Houston.

The wedding took place in a "large, open-air tent" before the Delta variant was circulating widely in the US. Guests were required to be fully vaccinated at the event, though that policy operated on the honor system.

The study's authors said they suspect the Delta variant was introduced at the wedding by two people who had traveled from India and tested negative before their flight but developed symptoms in the U.S. All the Covid-19 patients said they'd had close encounters with those two people during the wedding, according to the study.

All six guests who contracted symptomatic COVID-19 after the wedding were over 50. Two had gotten the vaccine from Pfizer, two had gotten the vaccine from Moderna, and two had gotten an Indian-made vaccine called Covaxin, the study said. Their infections were confirmed with lab tests and viral sequencing for Delta, it said.