Doctors move to reassure patients after vaccinators accidentally use half doses of Covid boosters

Knockin Medical Centre moved to reassure patients to say that none of them had come to any harm and to urge them not to try and arrange any extra appointments, saying that getting a further half dose could "theoretically" increase the risk of heart trouble.

In a letter to patients who had received a half dose, the centre's senior doctors said they considered the incident an "important learning event", and that the person who had been administering the half dose was "upset and concerned" about the mistake.

The letter, dated October 25, said: "It has come to light that one of our vaccinators has inadvertently been administering half the recommended dose of the Spikevax Moderna bivalent vaccine (Covid booster). As a result, you have only received 0.25mls instead of the recommended 0.5mls.

"As soon as the error came to light, we sought advice from our regional vaccination team. They communicated with NHS England who had reports of the same incident having taken place in several locations throughout the UK."

It is not yet clear how many patients received half doses, or how long the half doses were being administered before the mistake was detected.

The letter went on: "The advice from NHS England, who have liaised with the UKHA national vaccination team, is that you remain protected and are adequately vaccinated. You should not seek additional vaccination and your next vaccination should take place no earlier than planned.

"This is important from a safety point of view, and it is the case for all categories of patients, even those who are immunosuppressed. There is a concern that a further half dose to make up the full dose could theoretically increase the risk of serious cardiac side effects.

"Although you have not come to harm from this, we felt it was important to be open and honest and to let you know. I hope this letter has not caused you any unnecessary worry.

"We consider such incidents as important learns events which we should reflect over and to make changes to prevent further mistakes.

"Whilst all vaccinators undergo learning modules before proceeding to vaccinate patients, there is increasing complexity over Covid vaccination. The vaccinator who administered the 50 per cent dose has reflected over the event. He was upset and concerned to have made such an error and has reviewed all learning associated with vaccinations.

"As a practice, we are responsible for all clinicians and thereby take responsibility for this mistake. We have reviewed our practice procedures and have determined that two clinicians from the practice will, in future together make a check, prior to rollout of vaccinations, so that all staff are clear what dose of vaccine should be administered.

"This event will be recorded on Pinnacle, the national electronic database of NHS patient details. We will also ensure a record is entered into your medical records. Please accept our apologies for this incident."