As a physician in a Covid-19 care unit, I celebrate the vaccines as one of medicine's greatest triumphs. They provide extraordinary protection against severe disease and death, and are the world's best option for returning to a more normal life. As a scientist and lead investigator for a study on Covid-19 immunity, I have also come to appreciate the significance of so-called natural immunity acquired by those who have had Covid-19, and the power of “hybrid immunity” — the protection gained when such people also get vaccinated.
