Warren Buffett is this year bringing back the annual extravaganza for shareholders of his Berkshire Hathaway Inc that he calls "Woodstock for Capitalists."

But the 91-year-old billionaire has a cautionary message: If you want to attend, get vaccinated against COVID-19.

Proof of vaccination will be required to attend Berkshire's annual meeting in a downtown Omaha, Nebraska arena on April 30, and to shop from Berkshire-owned businesses in an adjacent exhibit hall.

The meeting is the centerpiece of three days of events across Omaha including shopping discounts, an outdoor picnic, and a 5-kilometer run that typically attract some 40,000 people from around the world, including large numbers from China.

Many go to reconnect with friends and share investment ideas. "It's a tuition-free course in Investments 101," said Tom Russo, a principal at Gardner Russo & Quinn who said he plans to attend his 35th meeting this year.

Before the pandemic, it was common for people to camp out overnight before the arena's 7 a.m. opening, so they could get good seats.

"It's a weird combination of trade show and press conference and celebration of capitalism," said Jim Shanahan, an Edward Jones & Co analyst who has gone twice. "A lot of people are looking forward to attending, me included."

Berkshire scrapped the weekend in 2020 and 2021 because of the pandemic, while streaming truncated annual meetings online. This year's meeting will also be live-streamed.

Buffett and Vice Chairman Charlie Munger, 98, will field five hours of shareholder questions with a break for lunch, with Vice Chairmen Greg Abel and Ajit Jain joining them in the morning.

In his annual letter to Berkshire shareholders, Buffett also said the "Margaritaville" singer Jimmy Buffett (no relation) has designed a "pontoon 'party' boat" now being built by Berkshire's Forest River unit. It will be available for sale, at 10% off.

"Your bargain-hunting chairman will be buying a boat for his family's use," Buffett wrote. "Join me." (Reporting by Jonathan Stempel in New York; Editing by Cynthia Osterman)