BOSTON (CBS) — The Delta variant now accounts for the vast majority of new coronavirus cases in the United Kingdom, where hospitalizations and deaths continue to climb. Dr. Mallika Marshall is here to answer questions about the latest COVID-19 variant.

Q: Doctor, the good news is that the vaccines seem to be making a difference? 

A: Yes. The Delta variant is more transmissible and may cause more severe disease than previous variants but only 8% of the total number of people infected with the Delta variant in the U.K. had received both doses of vaccine.  The majority of those hospitalized were unvaccinated or partially vaccinated, suggesting that the vaccines, though not perfect, are working and cutting down on severe illness.

Q: What does the experience in the U.K. mean for us here in the U.S.?

A: Experts say the U.S. is usually about one-to-two months behind the U.K. in terms of coronavirus cases.  Right now the Delta variant makes up about 20% of cases in the U.S. but that number will continue to climb exponentially.  And hospitalizations and deaths will be especially bad in pockets of the country where vaccination rates are low.

Q: There has been some concern about how protective the vaccines are against this highly contagious Delta variant.

A: Studies have suggested that two doses of the Pfizer vaccine is 88% effective against symptomatic illness.  It’s not clear just how effective the J&J vaccine is just yet, but the company says it’s looking at that.  However, data from the U.K. suggests that a single dose of a coronavirus vaccine is not nearly as effective as two doses, leading some experts to believe that people who have received the one-shot J&J vaccine may need a booster sooner rather than later.  Stay tuned for more on that.

Q: And we know that 1 in 10 people who received their first dose of the Moderna or Pfizer vaccines have skipped their second dose.  This is even more reason for those people to get their second dose as quickly as possible, right?

Yes. Please don’t hesitate. You’re not well protected by getting just one dose of either of those vaccines.

Q: What would you say to people who are wondering whether they should start wearing masks routinely again?

A: No vaccine is perfect. And there will be some people who are fully vaccinated who will get infected, so if cases in your area begin to rise or you’re in a region of the country where vaccination rates are low, continue to wear your mask even if it’s not required, socially distance, and use proper hand hygiene.  I will always recommend you err on the side of caution.  And listen carefully for updates on if and when you should receive a booster dose.

If you have a question for Dr. Mallika Marshall, email her or message her on Facebook or Twitter.

Dr. Mallika Marshall