Even if the US (or any other country) thinks it has reached herd immunity, global travel could introduce new variants and wreak havoc again.
That could be especially dangerous if a new variant compromises the effectiveness of vaccines or re-infects those who have been previously infected.
“Herd immunity will not happen until there is global immunity,” [physician Jorge] Rodriguez said.
Dwindling immunity — either from previous infection or from vaccination — could be another reason the US could slip in and out of herd immunity.
“We don’t know how long immunity from natural infection lasts,” Rodriguez said.
“I’ve had patients that have been infected, and we check their antibodies a month later, and they’re gone … I’ve had patients who got infected in the first surge, and they still have antibodies. But it’s very unpredictable,” he said.
“We also don’t know yet how long we’re going to have immunity from being vaccinated. We don’t know if it’s a year. We don’t know if it’s 9 months.”
The most important step is to get vaccinated, Rodriguez said.
“By maximizing vaccinations, we can minimize infectivity and mutations,” he said.
“The more we vaccinate, the less likely we are (going to slip in and out of herd immunity) because there’s going to be less replication.”