Caution should be taken over extending the gap between doses of Covid-19 vaccines, various senior medics and experts have urged.
Dr Denis McCauley, GP chair of the Irish Medical Organisation (IMO), said the move would be “unjustifiable medically and morally” if taken before the most vulnerable are vaccinated.
The Irish Times reports that experts have warned a significant benefit to the vaccination programme would be needed to justify an extension, after the Minister for Health sought advice on the possibility.
Dr McCauley said he believed an extension of the gap would not greatly speed up the State’s vaccination programme and modelling showing an “enormous, obvious difference” would have to be published to justify the move.
He added that the step should not be taken until after the very vulnerable are fully vaccinated with a four-week gap between doses.
“To delay their 90 per cent coverage [the efficacy reached from two shots] would be unjustifiable medically and morally,” he said.
Some experts support increased dosage intervals. Luke O’Neill, professor of immunology at Trinity College Dublin, said more first doses would protect more of the population against severe disease.
However, vaccine specialist Anne Moore, senior lecturer at UCC’s school of biochemistry, said extending the gap was not supported by clinical trial research.
“My core belief is that we should stick with the clinical evidence that was generated in the clinical trials by the companies that are manufacturing the vaccines,” she said.
Anthony Staines, professor of health systems at Dublin City University, also warned that extending the gap would increase the risk of spreading vaccine-resistant coronavirus strains.
“It’s not mad, bad or wicked to do something different, but the safer approach is to do what we are doing,” he said.
The State’s acting chief medical officer, Dr Ronan Glynn, said there were pros and cons to the extension but “it would mean that the programme overall will finish later, and for a large number of people they’ll be waiting longer to be fully vaccinated”.
A decision on the extension will not be made until later this week, when the European Medicines Agency (EMA) concludes a review on the one-shot Johnson & Johnson vaccine after it was potentially linked to rare clotting events.
Limitations on the use of the vaccine would further impact the State’s vaccination programme, with the AstraZeneca vaccine already restricted to use in those over the age of 60.
Government sources have said that all options, such as the extension of dosage intervals, have to be considered to keep the vaccination programme on track and allow for more restrictions to be lifted amid uncertainty over vaccine availability.
However, senior public health officials believe spacing out doses might only accelerate the vaccination programme by two or three weeks — unless it was significantly increased well beyond the manufacturers’ guidelines of up to six weeks.