Can vaccination and infection rates add up to reach COVID-19 herd immunity?

It’s been a long, dark winter of Covid-19 concerns, stoked by high post-holiday case counts and the American death tally exceeding 530,000 lives lost. But with three vaccines — Pfizer-BioNTech, Moderna and Johnson & Johnson — now authorized for emergency use in the United States, there seems to be hope that the pandemic’s end may be in sight.

A recent analysis by the Wall Street research firm Fundstrat Global Advisors fueled this idea, suggesting as many as nine states were already reaching the coveted "herd immunity" status as of March 7, signaling a return to normal was close at hand.

"Presumed ‘herd immunity’ is ‘the combined value of infections + vaccinations as % population > 60%,’" noted a tweet by a CNBC anchor based on a more complete analysis by the firm. But that got us thinking: Does this calculation hold up?