Though vaccination rates are improving and booster shots will soon be available in the U.S., there is still much to be learned about how the coronavirus is evolving.

“We have a higher level of uncertainty now than we’ve had since the spring of last year,” Dr. Howard Forman, professor at the Yale School of Public Health, said on Yahoo Finance Live (video above). “Because there are so many moving parts, we don’t know whether the vaccines are causing waning immunity or rather whether waning immunity is occurring.”

Some U.S. states are seeing hospitals overwhelmed with mostly unvaccinated individuals with COVID-19, and some government leaders have reverted back to measures that were implemented at the onset of the pandemic in order to mitigate the spread.

“Governors and mayors have a lot of responsibility to manage their own locale as best they can, which may include masking, may include other measures,” Forman said. “We have to hope they take those measures at the right time to mitigate as much as possible. What’s going to happen after this wave is unknown to anybody. We’re really still very much in the dark.”

'We just have much more uncertainty than we would like'

The Delta variant, a mutant strain of the virus that has proven to be significantly more contagious than the original strain, now accounts for over 98% of coronavirus cases in the U.S.

Nevertheless, Forman cautioned against questioning the effectiveness of the vaccines, especially since they were developed at a time when the Delta variant didn’t yet exist.

“Protection against infection appears across the board lower than we expected,” Forman said. “But that may be more about Delta than it is about the vaccines. The combination of these things means that we just have much more uncertainty than we would like to have.”

Though fully vaccinated individuals can experience breakthrough infections against the Delta variant, an overwhelming majority are still protected from the most serious effects of the virus.

“I would just caution people that the vaccines are actually holding up very well against severe disease and death,” Forman said. “Not as well against incidentally asymptomatic or mild infections.”

'Have a little bit of caution right now'

Though preliminary data has indicated that booster shots could make a difference in developing immunity, specifically for the elderly and other vulnerable populations, Forman urged others to be patient about waiting their turn.

“People are already going out for shots and basically misleading or just not telling the centers they’ve already been fully vaccinated,” Forman said. “I would just tell people to have a little bit of caution right now about doing that so easily. The immunocompromised population is one that we have really good data that they did not respond well to two shots in the case of the mRNA vaccines or one shot with J&J. We had really good evidence of that.”