As vaccination efforts ramp up across the United States, reports of two new COVID-19 variants have emerged. These variants, first identified by researchers in California and New York, are raising concerns about vaccine effectiveness and higher transmission rates.

The California variant, B.1.427/429, was first found by a couple teams of researchers in small numbers in Southern California in late 2020. By mid-January, it made up half the cases in the area. Now, according to their reports, it has become dominant in California.

Preliminary findings from two new UC San Francisco studies on this variant suggest it is more infectious than previous strains of COVID-19. Since its discovery, the variant has been detected in other states, but it remains concentrated in California.

The variant in New York City, B.1.526, was first identified in November and now accounts for approximately a quarter of the cases in the city, according to a pre-print of a study from the California Institute of Technology.

While it doesn’t appear to be spreading as rapidly or as widely as the California variant, this variant is attracting attention because it contains a similar mutation to the South African variant, B.1.351, and may be better at bypassing the body’s immune response. The vaccine’s efficacy against variants with this mutation has been questioned.

While the research into both variants has yet to undergo peer review, the initial findings are being taken into consideration by public health experts.

White House Chief Medical Advisor Dr. Anthony Fauci says the New York variant is being taken “very seriously.”

Reports of these new variants come after a recent decline in the number of new cases, hospitalizations and deaths across the U.S.

Kentucky Gov. Andy Beshear announced an eighth straight week of declining case numbers and a positivity rate under 5 percent, the lowest since September. This resulted in eased restrictions for businesses across Kentucky. Beshear also addressed concerns over the variants.

“We’re going to be watching closely,” Beshear said.