Restaurant Brands International (QSR  ), owner of Popeyes, Burger King, and Tim Hortons, released fourth quarter figures showing a surge in sales caused by the Popeyes chicken sandwich.

According to the report, sales at Popeyes franchises jumped 42% on average in the last three months of 2019 to $1.3 billion. For franchises open for at least 17 months, that number was slightly lower at 34%.

The sales boom was caused by Popeyes "biggest product launch in the last 30 years."

The Popeyes chicken sandwich, according to their website, is "A tender all-white meat chicken breast fillet, marinated in an authentic blend of Louisiana seasonings, then hand battered and breaded in our all new buttermilk coating. Served with crisp barrel cured pickles and Classic or Spicy Mayonnaise, served on a warm and toasted buttery brioche bun."

The sandwich was first launched in August of 2019. It sold out across the nation just two weeks after its launch. The "extraordinary demand" took the chain by surprise, but they quickly adjusted to the sandwich's popularity.

It was brought back in November after the fast-food chain took precautions to prevent shortage. Sales in the fourth quarter show that the fervor for the chicken sandwich continued into the fall.

According to a statement released by Restaurant Brands International CEO Jose Cil, the sandwich brought in customers who then spent money on other products.

"For the vast majority of our guests purchasing the sandwich, we saw that they actually spent more on other products. The traffic driven by the demand of the Popeyes Chicken Sandwich helped drive growth in our entire menu."

Cil also said in the statement that the boost in sales caused by the chicken sandwich has led U.S. franchise operators to consider opening new restaurants.

Meanwhile, competitors have been trying to ride the chicken sandwich wave. Wendy's (WEN  ) tried to compete by promoting its own version of the sandwich on Twitter (TWTR  ). McDonald's (MCD  ) has been testing fried chicken sandwiches since December in select markets, and they also offered chicken breakfast sandwiches nationally for a limited time.

The other two Restaurant Brands International restaurant chains may not have boomed as much as Popeyes, but Burger King, at least, has found its own niche.

According to Cil, the newly offered Impossible Whopper, a plant-based alternative to the traditional Whopper, was "important sales driver." Fourth quarter sales jumped 8% to $5.9 billion. That number was lower at 3% growth in franchises open at least 13 months.

After the positive reception the Impossible Whopper received, Burger King plans to introduce more plant-based offerings to their menu.

Tim Hortons (THI  ), on the other hand, is struggling. The report showed fourth quarter sales down 3% on average and 4% in cafes open at least 13 months.