A version of this story appeared in the March 26 edition of CNN’s Coronavirus: Fact vs. Fiction newsletter. Sign up here to receive the need-to-know headlines every weekday.The study, detailed in the journal Nature Medicine on Thursday, may explain why so many people infected lose their sense of taste, and suggests the mouth is an important source of the spread of Covid-19. It was previously known that saliva testing was a good way to detect infection, but researchers hadn’t looked to see why. “When infected saliva is swallowed or tiny particles of it are inhaled, we think it can potentially transmit SARS-CoV-2 further into our throats, our lungs, or even our guts,” said Dr. Kevin Byrd of the American Dental Association Science and Research Institute, who worked on the study. The mouth, nose, sinuses, throat and lungs are connected, and the virus can spread across all those regions in mucus that drains or is coughed up. They checked samples of oral tissue from people who died of Covid-19 and found the virus in about half of the salivary glands they tested. The study also found evidence that people who test negative after a nasal swab sometimes continue to test positive on a saliva test, highlighting that even if the virus is cleared from the nasopharynx — the upper part of the throat behind the nose — it could persist in saliva. YOU ASKED. WE ANSWERED. Q. Can pregnant or breastfeeding women get a Covid-19 vaccine?A. This depends on what country you’re in. In many parts of the world, Covid-19 vaccines are unavailable to pregnant women, and breastfeeding women in some places are advised against being inoculated, because of a lack of data on these groups. In the US, the CDC has not advised pregnant and breastfeeding women to take the vaccine, but allows them to access it, arguing it is a woman’s choice on how to balance the benefits and risks.A new study suggests the Pfizer/BioNTech and Moderna Covid-19 vaccines used widely in the United States are at least effective for these women and even their unborn babies. Researchers at Massachusetts General Hospital, Brigham and Women’s Hospital and the Ragon Institute of MGH, MIT and Harvard looked at 131 women who received either of the shots. The vaccine-induced antibody levels were equivalent in pregnant and lactating women, compared to non-pregnant women, the study shows. The team also found that breastfeeding women passed protective antibodies to their newborns. Send your questions here. Are you a health care worker fighting Covid-19? Message us on WhatsApp about the challenges you’re facing: +1 347-322-0415.WHAT’S IMPORTANT TODAY Dangerous variants could mean ‘all bets are off’ in US recovery As US states relax restrictions and Americans start traveling again, medical experts are warning that the pandemic is far from over and that new variants threaten to derail progress in the country.A rise in infection numbers in several states “tells us when we have a more contagious variant that all bets are off because it means that the activities that we thought were pretty low risk are now going to be higher risk,” CNN medical analyst Dr. Leana Wen told CNN’s Anderson Cooper on Thursday. Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, also warned on NBC’s “Today” show that the US is “still seeing about 1,000 deaths a day,” which is “way too many.”President Joe Biden doubles vaccine target for first 100 daysThe United States has one of the fastest vaccination rollouts in the world, with 133 million doses already administered. Building on that momentum, President Biden said Thursday his administration was aiming to have 200 million doses administered by the end of April, doubling his original target.”I know it’s ambitious — twice our original goal — but no other country in the world has even come close, not even close to what we’re doing. I believe we can do it,” Biden said.EU summit descends into squabbling as leaders dial up pressure on AstraZeneca and the UKA summit that was supposed to push drug company AstraZeneca to speed up its deliveries of tens of millions of vaccines and pressure the UK into sharing doses made in the country was hijacked by Austrian Chancellor Sebastian Kurz, who demanded a greater share of shots for his people, creating an internal rift in the bloc.European Union leaders at the virtual meeting confirmed their plans to allow a ban on export vaccines in some situations to keep doses from leaving the bloc’s shores, as it struggles to roll out a widespread vaccination program.ON OUR RADARDream of sipping a margarita in Mexico? You can visit I Miss My Bar, an interactive website that brings the atmosphere of the bar Maverick in the city of Monterrey. Officials in the Seychelles are pulling out all the stops to ensure travelers can return quickly and, more importantly, safely.Some workplaces, colleges and hospitality venues may demand vaccine certificates to allow entry. Rutgers University is one of the first in the US to require vaccines for students this fall. Covid has a color, Catherine Powell writes. The pandemic has highlighted a range of underlying inequalities on race — including on the job front — exacerbated by the health crisis and the emerging stay-at-home economy. The US government has stopped distribution of the Covid-19 antibody treatment developed by pharmaceutical company Eli Lilly, as authorities say the therapy on its own may not work as well against new variants.TODAY’S PODCAST “Only once we’ve really gone through this period where we’ve tried very hard to improve voluntary uptake, should we then start to think about mandates being necessary and appropriate.” — Emily Largent, lawyer and assistant professor of medical ethics. Suppressing the spread of Covid-19 in the United States is going to require vaccinating 70-85% of the population. But what happens if not enough Americans voluntarily get the vaccine? CNN’s Chief Medical Correspondent Dr. Sanjay Gupta talks to Largent about a controversial proposal that’s been floated: mandating the vaccines. Listen now.