With coronavirus cases spreading rapidly throughout California and the nation, reports of infections among those who are fully vaccinated for COVID-19 are increasingly drawing attention.

But while these “breakthrough” cases are sometimes highlighted as a precautionary tale — a signal of the shots’ shortcomings — the reality is that the vaccinations remain as consistently effective as ever where it counts: protecting people against severe illness.

That remains true, officials say, even as Los Angeles County health officials shared a seemingly ominous data point Thursday: 20% of newly diagnosed coronavirus cases in June occurred among vaccinated people. Less than two weeks ago, they said over 99% of COVID-19 cases were among the unvaccinated.

At first blush, these numbers may seem to disagree with each other. But a closer look at the data underscores some key findings cited by public health experts, epidemiologists, and infectious disease experts in California and by federal officials.