Booster shots of the Pfizer and Moderna COVID-19 vaccines are available for certain people with weakened immune systems, and federal officials are closing in on authorizing third jabs for millions more. Advisers to the Centers for Disease Control and Prevention said Wednesday that boosters of Pfizer’s vaccine should be offered to people 65 and older, nursing home residents and those ages 50 to 64 who have risky underlying health problems. The extra dose would be given once they are at least six months past their last Pfizer shot. All three of the COVID-19 vaccines used in the U.S. are still highly protective against severe illness, hospitalization and death, even amid the spread of the extra-contagious delta variant. But only about 182 million Americans are fully vaccinated, or just 55% of the population. The vaccination rate in Massachusetts is above 65%.BREAKTHROUGH CASES IN MASSACHUSETTSMassachusetts public health officials track the number of COVID-19 cases among people who’ve been fully vaccinated against the virus. These are often called “breakthrough” cases and their rise in the face of the contagious delta variant has contributed to interest in the idea of booster shots. Breakthrough infections can cause disease with symptoms, and some people can have no symptoms at all. Research has shown that if people become infected after vaccination, typically they get a milder case.Officials began to publish data about breakthrough cases routinely during August. RATE OF COMMUNITY TRANSMISSIONThe U.S. Centers for Disease Control and Prevention has created a four-tier system to indicate the rate of transmission of COVID-19 in every county.Blue = LowYellow = ModerateOrange = SubstantialRed = HighCOVID-19 VACCINATION DATAAnyone age 12 or older who lives, works or studies in Massachusetts is eligible to be vaccinated.Based on federal approvals, the two-dose Pfizer vaccine is available to anyone age 12 or older as of May 13. The two-dose Moderna vaccine and the one-dose Johnson & Johnson vaccine are available to those age 18 or older.VACCINATION RATES AMONG ELIGIBLE POPULATIONMassachusetts has fully vaccinated more than 4.6 million people. According to the 2020 U.S. Census, the state’s total population is 7.03 million.State directory of vaccination sitesVACCINATION RATE COMPARED TO OTHER STATESMASSACHUSETTS CORONAVIRUS CASESSymptoms reported for patients with COVID-19 have included mild to severe respiratory illness with fever, cough, and difficulty breathing, as well as new loss of taste or smell. Further details are available here.This state website will help you locate the nearest COVID-19 testing facility. Massachusetts also has an online resource that allows you to assess your symptoms and find the right care.For more information on coronavirus and testing, you can also call 211, which is a 24-hour state-supported hotline.MASSACHUSETTS HOSPITALIZATIONSIf you develop emergency warning signs for COVID-19 get medical attention immediately, the CDC said.Emergency warning signs include:Trouble breathingPersistent pain or pressure in the chestNew confusion or inability to arouseBluish lips or face*This list is not all-inclusive. Please consult your medical provider for any other symptoms that are severe or concerningMASSACHUSETTS FATALITIES