Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC), expressed concern Wednesday that unvaccinated people will suffer preventable COVID-19 sickness and death due to the seasonality of the virus.

Federal data indicates 51.7% of U.S. adults are fully vaccinated as much of the country shifts into warmer summer months. Walensky, speaking virtually at the 9th annual Atlanta Global Health Summit, said coronaviruses tend to have seasonality, and respiratory viruses tend to favor the winter months.

"In terms of seasonality, we certainly did see a summer surge in areas last year where people were indoors and the hot states, and this winter surge after travel."

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Data compiled by the World Health Organization on weekly cases indicates the United States was logging some 460,000 infections during summer-time highs in mid-July, before increasing to millions of new infections reported each week in the late fall and winter.

"I am really hopeful that we will have vaccinated enough of the country that we won’t see these large spikes, barring any challenges associated with variants," she said. "In addition to the seasonality, what concerns me is the heterogeneity of where we are across the country because this virus is going to be an opportunist. And it may not go to places in California that are 70% vaccinated, but it may well go to places in Georgia that are 20% vaccinated."

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Walensky warned over preventable illnesses and poor outcomes.

"What I really want to do is try and see if we can blanket as much vaccine to places that are undervaccinated, so that when this  —should this — rear its ugly head again, shall we say… that it’ll hit some stopping points because we have a chunk of people who really are vaccinated."

"I really would be saddened to see that we had to see more communities see sickness before those communities got vaccinated, I worry about that and we do know it’s the individual who’s going to get sick."

According to Andy Slavitt, the White House's senior COVID advisor, Maryland and California recently joined a list of 10 other states with 70% of the adult population to receive at least one dose of vaccine.