Coronavirus booster shots not necessarily the answer

Expert opinion unsure if ‘a three-dose schedule will improve responses, or durability’

From boasting about the massive uptake of our Covid-19 vaccine rollout, the focus has suddenly switched to analysing its shortcomings.

With case numbers tilting upwards again, and hospitals filling up with virus patients, officials are searching for ways to control the latest acceleration in the spread of the virus.

Just over a week ago, National Public Health Emergency Team official Prof Philip Nolan said Ireland was "close to suppressing" the disease. Yet on Thursday, he described the situation with the virus as being "on a knife-edge".

Total doses distributed to Ireland Total doses administered in Ireland
12,143,670 10,222,511

People could be forgiven for being bewildered, given the scale and speed of the about-turn by public health officials, but things move fast in Covid-land, especially with the highly transmissible Delta variant.


Mass vaccination, despite not succeeding in driving down case numbers, has allowed Irish society to return to near normality as the year went on. Understandably, therefore, “more of the same” is seen as the best bet for containing the present situation.

There are good reasons, however, for believing this approach will struggle to produce results.

According to the European Centre for Disease Control’s (ECDC) tracker, 91.8 per cent of the Irish adult population is fully vaccinated. That’s the highest figure in the EU, and well above the European average of 74.7 per cent.

We’re also a leader across the continent in the vaccination of vulnerable groups. For example, 100 per cent of over-80s in Ireland are recorded by the ECDC as being fully vaccinated (estimates are slightly inflated due to the use of 2016 Census figures).

With so many now vaccinated, the pace of the rollout is understandably reduced from earlier months. The number of new first doses administered each day is in the hundreds now; 785 on Wednesday, 652 on Tuesday.

The success of the rollout leaves few enough unvaccinated arms to find. According to deputy chief medical officer Dr Ronan Glynn, there are almost 300,000 adults who are not vaccinated.

However, polling has shown that about 5-8 per cent of adults say they will definitely not get vaccinated. It would appear most of those still unvaccinated belong to the “anti-vax” category and are likely to be resistant to all appeals for a change of mind.

There are 70,000 people who have received just one dose and some of these might be persuadable to come in for a second dose. Uptake among groups such as pregnant women, who are at a demonstrable risk from the virus, could be improved by offering vaccines on-site, at the same time as prenatal check-ups. A similar outreach approach could work with at-risk groups, particularly Travellers, among whom there are currently a high number of outbreaks.

To double down further on the unvaccinated, however, is to risk the consensus approach that has served us well so far. Some groups feel they have little to fear from the virus, by dint of their youth or recent infection. We can ask them to get vaccinated for the wider good of society, but such a “Green jersey” approach hasn’t served us well in the past.

Politicians also appear to be pinning their hopes on the wider use of booster shots, which up to now are only recommended for over 80s, residents of nursing homes and the immunocompromised.

Specialist view

This is despite a lack of evidence – so far - for age-based boosters, and the clear advice of the World Health Organisation that vaccines should be used in the first place in the developing world, where supplies are scarce.

As consultant immunologist Prof Mary Keogan told an RCPI symposium on Thursday, "we don't know if a three-dose schedule will improve responses, or durability" of protection.

Prof Keogan, who believes “we’re at the end of the beginning [of the pandemic] but we’re not there yet”, noted that there is a responsibility to use scarce resources prudently.

Even if everyone was vaccinated, that would only halve the numbers in hospital and intensive care. That points to the need for a “vaccine-plus” approach for the coming months, incorporating the minimum number of protections needed to keep the virus at bay.