With rising cases of COVID-19 across the country and at least two new mutant strains of the virus identified, the U.S. is aiming to make sure every eligible American gets a coronavirus vaccine.

“We are really in a race against those variants and the case count to vaccinate as many people as possible,” Dr. Rachael Piltch-Loeb, an associate research scientist at the NYU School of Global Public Health, told Yahoo Finance Live (video above). “I think that is what’s underlying the shift in strategy that’s coming out of the Biden administration.”

President-elect Joe Biden has stated that upon taking office, he will ensure that all available doses of the vaccines are released to the public. On Tuesday, the CDC shifted its guidance to recommend anyone over the age of 65 be vaccinated as the rollout been slower than expected.

“I think the rationale for increasing or shifting the dose strategy has a lot to do with the fact that we need to get as much vaccine into as many people’s arms as quickly as possible,” Piltch-Loeb said. “With the new variant that’s taking hold from the U.K., as well as the variant that seems to be coming out of Africa, more infectiousness, higher infectiousness, means that there’s likely to be more cases, which means our health system is likely to be overwhelmed.”

‘The day you get the vaccine is not the day you are immune from COVID-19’

Many hospitals and ICUs are already overwhelmed.

In Los Angeles, the most populous area of California, some ambulances have been turned away from emergency rooms because they have reached capacity, and mobile morgues are stationed outside in parking lots.

“We’re in for a challenging couple of months,” Piltch-Loeb said. “Many public health experts are echoing the same sentiment. Unless we take dramatic measures to either lock down or shift the way in which we’re able to get vaccines to people in a much more rapid capacity, it’s going to be a challenging couple of months.”

In most states, only long-term care residents and front-line health care workers are eligible to get vaccinated right now. However, the criteria is slowly expanding, though some have worried the current vaccines from Pfizer (PFE) and Moderna (MRNA) won’t work against the new strains. But studies so far have indicated that they will be effective.

“The latest evidence seems to suggest that the vaccine can still work against the new variants, but anything is possible,” Piltch-Loeb said. “And we know that viruses continue to mutate, and we know that there may come a time when the vaccine has limited effectiveness towards whatever the new variants may be. So the goal is just to move as quickly as possible, recognizing that the vaccine we currently have should work against the strains that we’re seeing.”

Even if someone is vaccinated, though, public health officials, including Piltch-Loeb, are urging them not to let their guard down yet.

“What’s important to remember is the day you get the vaccine is not the day you are immune from COVID-19,” Piltch-Loeb said. “And so, there’s still that window by which when people get vaccinated, that they may still be able to get the virus, to spread the virus.”

“Immunity doesn’t develop just immediately,” she added. “So we’re in for a challenging couple of weeks, even with the vaccine, based on the strains that we’re seeing, maybe perhaps a couple of months. But again, it emphasizes that speed is really critical here.”

Adriana Belmonte is a reporter and editor covering politics and health care policy for Yahoo Finance. You can follow her on Twitter @adrianambells.

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