By Tim Mastro

DOVER — The Pfizer vaccine has led to the most breakthrough cases of COVID-19 in Delaware, although positive cases in fully vaccinated individuals continue to be rare.

Of Delaware’s 383 breakthrough cases as of Thursday, 240 had received the Pfizer vaccine, according to the Delaware Division of Public Health. The next highest was 75 cases in individuals who had taken Moderna, while the remaining 68 were the one-dose Johnson & Johnson vaccine.

Pfizer is the most common vaccine in Delaware, which could explain the larger number of breakthrough cases compared to the others. Delaware has been allocated 655,575 doses of Pfizer, compared to 498,020 of Moderna and 62,700 of J&J.

Pfizer is also the vaccine that has been administered for the longest period of time, as it was approved for emergency use Dec. 11.

With 427,602 residents fully vaccinated in Delaware, the 383 breakthrough cases make up less than 0.1% of that population. The First State has recorded an all-time total of 109,564 positive cases of COVID-19 — 109,181 of which have come in individuals who are not fully vaccinated.

The DPH said a breakthrough case is “defined as testing positive for COVID-19 after an individual has been fully vaccinated for two weeks or more — although it does not mean that the infection actually occurred after vaccination.”

According to the U.S. Centers for Disease Control and Prevention’s vaccine tracker, 68.9% of Delawareans 18 and older have received at least one dose of a COVID-19 vaccine. This number differs from the DPH’s tracker because the CDC includes Delawareans vaccinated in other states, as well as in locations like Veterans Affairs facilities and Dover Air Force Base — entities that do not report their numbers to the DPH.

There have been 981,514 doses of vaccine administered in Delaware, as of Sunday at 6 p.m. Delaware has used 80% of its 1,216,295 doses, which includes 827,280 vaccines shipped directly to the state and 389,015 via federal pharmacy programs.

No new COVID-19-related deaths were reported by the DPH in Monday’s update, so that total stayed at 1,683. COVID-19 hospitalizations tied their lowest mark since DPH began providing the data — down to 22, with four cases considered critical.