A new study underscores the need to get both doses of COVID-19 vaccines. Scientists found that 2 doses are needed to provide protection against the variants first identified in India. The same rule applies to neutralizing the British variant, say researchers.

According to CNBC, both doses of the 2-dose vaccines made by Pfizer-BioNTech and AstraZeneca are required to effectively protect against the variants. Dr. Jenny Harries, OBE, the chief of the U.K. Security Agency, told the BBC that the new study provided the "first real-world evidence of vaccine effectiveness" in neutralizing the variants that are rapidly spreading.

The study conducted by Public Health England between April and May found that the Pfizer-BioNTech vaccine was 88% effective against symptomatic disease from the B.1.617.2 coronavirus mutation that originated in India last fall and has since spread globally. The same vaccine was 93% effective against the British variant, B.1.1.7, according to CNBC.

Two doses of the AstraZeneca shot proved to be 60% effective against the Indian variant and 66% protective from symptomatic disease against the U.K. mutation. One of the key findings was that 1 shot of both drugs were only 33% effective against the B.1.617.2 virus 3 weeks after the first dose, and 50% effective against the B.1.1.7 variant.

Previous studies have shown the two doses of the mRNA Moderna COVID-19 vaccine can also protect against the variants.

According to Business Insider, the B.1.1.7 mutation that was first detected in the U.K. and has now spread to the U.S., was evaluated by several university and hospital research teams and found to be between 30% and 70% more lethal than SARS-CoV-2, the original coronavirus responsible for COVID-19.

Earlier research discovered that the variant doubles every 10 days and is also 35% to 45% more transmissible than other strains currently circulating in the U.S. The BBC says the transmission rate of the variant from India is roughly 50% higher than for the U.K. version. The World Health Organization said recently that this new COVID-19 strain is a "variant of concern."

Experts have repeatedly warned that both doses of the vaccine are crucial to staving off serious disease from COVID-19.

According to Good Housekeeping, Dr. Nicholas Kman, an emergency physician at Ohio State University’s Wexner Medical Center, said getting both shots ensures as much immunity as possible against the virus.

Research has shown that getting only 1 shot of the Pfizer drug provides 52% defense against the spread of the virus and the first shot of the Moderna vaccine imparts 80% protection. But there are no clinical studies to show how long partial protection lasts. Kman says that while both vaccines do provide some protection against a person becoming infected by the virus after the first dose, the second dose increases the number of antibodies in bloodstream tenfold, offering 95% efficacy.

Dr. Anthony Fauci, the director of the National Institutes of Allergies and Infectious Diseases, questions whether one shot of the vaccine can provide long-term immunity, according to Good Housekeeping.

"When you leave it at one dose, the question is, how long does immunity last?" he asks. The infectious disease expert warns that with the new variants on the scene, "You’re in a tenuous zone if you don’t have full impact."