A year after the vaccine was given, the researchers found, its effectiveness waned, slipping from an average of 97 percent to 84 in years two through eight.

But Schmidt's effectiveness waned as his pitch count climbed.

Over his next 21 games, though, his effectiveness waned.

But its effectiveness wanes when employers set rules that obviously favor them.

Villone made a career-high 70 appearances last season, but his effectiveness waned under a heavy workload in August.

That's one reason why the effectiveness of older drugs often wanes when a new one comes along.

Gretzky was Team Canada's best player in the early part of the World Cup, but his effectiveness progressively waned.

Thigpen's effectiveness waned and he was supplanted in the closer role by Roberto Hernández.

The effectiveness of G.M.'s chairman is waning, regardless of whether he is removed.