It isn't easy to explain why Ireland, one of the most vaccinated countries in the world, also has one of the highest rates of Covid-19 infection.
The various possible factors for this remarkable non-achievement can be identified, but their relative contribution to the present outcome is difficult to ascertain.
Some of these factors are not unique to Ireland. Cases are soaring just now across much of Europe, which is the current epicentre of the pandemic. One of the main reasons for this is the onset of winter, with its damp weather, short days and enforced indoor culture.
The Delta variant has kept this pandemic going despite the development of new and effective vaccines. We used to worry about more lethal variants but the greater threat was posed by the more transmissible Delta variant because it infects so many more people.
We also knew vaccines would not work perfectly, but arguably the biggest disappointment is that they do not prevent onward transmission of the disease. Vaccinated people carry sufficient amounts of virus in their noses to pass on to others, even if they themselves are largely protected.
Vaccines do reduce transmission by about 20-60 per cent, according to different studies, and there is a further beneficial effect because fewer vaccinated people fall ill in the first place, but public health officials are explicit now on the limits to the protection they offer.
As early data from Israel has shown, their effectiveness in preventing infection tails off alarmingly after a few months, though they still protect against serious illness.
None of these factors explains why Ireland is in a worse position than just about anywhere else in western Europe at present. So what are the Ireland-specific factors at play?
First, we’re starting from a high base. Having suffered an early wave of Delta in the spring, we never managed to get case numbers down to low levels, as other countries did. Vaccination worked to keep the variant in check for months, before waning immunity and the reopening of society did their work.
Our public health officials also like to point to local differences that may contribute to greater spread of infection – our damp winters and younger population, and the relatively high proportion of intergenerational households. Also, our proximity to the United Kingdom, which has had higher case numbers than us for much of the pandemic.
But what about our relative remoteness, and few land borders, not to mention long lockdowns and high compliance with restrictions for so long since the start of 2020? Surely they must have helped keep the lid on the virus?
Some European states are benefiting from an earlier rollout of booster vaccines than has happened in Ireland. The benefits of boosters may turn out to be as time-limited as for the initial vaccine (or not; we won’t know until 2022) but if they help us get through the winter, they will have served their purpose.
Need a boost?
The latest data from the UK on boosters is very encouraging: more than 90 per cent effectiveness against infection compared with non-vaccination, more than 80 per cent added protection for those already vaccinated, and no safety concerns. British scientists are speculating booster protection might last “maybe up to next Christmas”.
Their latest update, published on Monday, also shows vaccine effectiveness against severe disease being sustained well beyond six months. So while many of us might not need boosters, the benefit they confer is in preventing disease and therefore cutting the general risk of severe disease.
The UK has until recently bucked the trend in Europe, despite getting rid of almost all restrictions months ago. Sweden has also done well this year, with far fewer restrictions than Ireland had.
Scientists have speculated this might be the result of high levels of immunity in their population, due to vaccination and past infection. In any case, both countries are seeing numbers increase again of late.
This is one of the features of this pandemic. In the words of the Frank Sinatra song, you can be "riding high in April, shot down in May". Ireland has gone from worst in Europe, to best, to worst again. In recent months, much of eastern Europe has experienced low numbers, and then record highs.
In summary, what we are seeing now is the result of increased social mixing, mostly indoors, affecting those with no or reduced protection through natural or vaccine-induced immunity.
The current wave will be brought under control when people mix less, or are better protected when doing so, and when immunity levels rise, through vaccines, boosters or infection.
* This article was amended on November 15th to correct a factual error