A breakthrough case is when an individual tests positive for COVID-19 after they’ve been fully vaccinated against the disease.
Numbers from the Massachusetts Department of Public Health show there have been 5,166 cases of COVID-19 in fully vaccinated individuals as of July 17, a significant increase from the 4,450 reported one week earlier.
As of Tuesday, the DPH reported 1,649 new positive COVID-19 cases between July 10 and July 16.
When analyzing the number of overall COVID-19 cases reported by the DPH between July 10 and July 16, the breakthrough cases account for 43.4 percent of all new COVID-19 cases.
Massachusetts doctors say the biggest cause is the arrival of the COVID-19 delta variant, which is twice as infectious than the original virus.