A Pennsylvania 17-year-old surprised her mom with a cake celebrating one of the mother’s important decisions.

Alyssa Jackson bought her mom a cake with “THX 4 VACCINATING US, MOM” written in icing on it.

"My sister and I went to pick up my vaccination records so I can switch my school, and we stopped at Dairy Queen for lunch," Jackson told BuzzFeed News. "After eating we were gonna get ice cream but decided it would be funny to make a TikTok of us getting that cake."

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The video shows a quick image of Jackson’s mother smiling in reaction to the cake.

The video went viral, earning more than 74,000 likes on TikTok as of this writing.

TikTok is a fast-growing social video app popular among teenagers. It has 500 million global monthly active users.

“I am happy that I’m vaccinated, because I have seen that some old-time diseases are coming back,” Jackson said. “I’m glad my mom hasn’t contributed to that.”

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Diseases like measles, which used to be eradicated in the United States, have been coming back. Doctors call this trend "unacceptable" because scientific research has found vaccines save lives.

study estimated vaccines protecting against 13 diseases have prevented more than 40,000 deaths.

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The FDA has said it may step in to strengthen vaccine laws.