U.S. pharmaceutical company Moderna said Monday its COVID-19 vaccine appears to produce virus-neutralizing antibodies against new variants of the coronavirus found in Britain and South Africa.In a statement, the company said it conducted studies to ensure the two-dose regimen of the Moderna COVID-19 vaccine is protective against emerging strains of the virus detected to date.  The company says it will continue a clinical strategy “to proactively address the pandemic as the virus continues to evolve,” including testing the effectiveness of an additional booster dose of its COVID-19 vaccine.That news comes a day after U.S. health officials said they are increasing efforts to track several COVID-19 variants emerging as the virus continues to spread throughout the world. U.S. Centers for Disease Control and Prevention chief Rochelle Walensky said in an interview Sunday the plan is to monitor “the impact of these variants on vaccines, as well as on our therapeutics.”  She said the CDC was collaborating with the National Institutes of Health, the Food and Drug Administration, as well as the Pentagon, in tracking the coronavirus mutations.The White House also said Sunday it is ready to restrict entry of non-U.S. citizens traveling to the U.S. from South Africa because of concerns about the highly contagious coronavirus variant that has emerged there.