They think it’s all over... It is not. Everyone would like to hear that the Covid-19 pandemic will soon be all over and we can all get back to ‘normality’. Thanks to the huge success of vaccine programmes, there are causes for optimism about the future. However, the only certainty about this pandemic is the uncertainty.
The emergence of variants of SARS-CoV-2, the virus that causes Covid-19, and the ability of vaccines to control them has been, and will continue to be, the single greatest factor that will determine the future direction of this pandemic.
With more than 78 per cent of adults fully vaccinated, why are there still so many cases in Ireland? The majority (74 per cent) of confirmed cases of Covid-19 are in those under 35 and many of these have not yet been fully vaccinated. However, about 3,400 of the 20,000 confirmed cases of Covid-19 (17 per cent) in the last two weeks were in fully-vaccinated individuals. Breakthrough infections are likely to be in those that have not responded effectively to the vaccines, in particular older people, those with compromised immune systems and/or those being treated with immunosuppressive therapies for a variety of other diseases.
There is inexplicable resistance by the Irish authorities to mixing vaccines
Statistics on the vaccine types associated with the infection breakthroughs in Ireland have not been provided. However, studies in other countries demonstrate that the mRNA vaccines (Pfizer and Moderna) are substantially more effective than adenovirus-vectored vaccines (AstraZeneca and Janssen) at inducing virus neutralising antibodies, the immune molecules that prevent the virus infection. The antibodies induced with all vaccines, but particularly the adenovirus-vectored vaccines, are less effective at neutralising the effects of the Delta and other variants of concern. This is consistent with clinical studies that report higher effectiveness of the mRNA compared with adenovirus-vectored vaccines against the Alpha, Beta and Delta variants.
There is inexplicable resistance by the Irish authorities to mixing vaccines, contrasting with international acceptance and implementation of this approach in many other countries. The scientific evidence unequivocally shows that boosting with a Pfizer or Moderna vaccine after a single immunisation with the AstraZeneca vaccine induces about 10 times stronger neutralising antibodies than two doses of the AstraZeneca vaccine and is associated with only small increases in transient mild-to-moderate side effects. The European Medicines Agency has said of this heterologous vaccination approach: “There are good scientific grounds to expect this strategy to be safe and effective when applied to vaccination against Covid-19.”
What does this mean for booster vaccination in Ireland? In my opinion, everyone over 70, high-risk individuals with certain underlying medical conditions and everyone who received the AstraZeneca or Janssen vaccines should be boosted with either the Pfizer, Moderna or, when supplies permit, the Novavax vaccine.
Recent studies have shown that infection with SARS-CoV-2 confers protection against reinfection which can persist for at least a year
I do not believe there is a case for boosting healthy individuals under 60 who have received two doses of an mRNA vaccine, at least until the new version of the vaccines designed to protect against the variants of concern are approved by the regulatory agencies. These modified vaccines have been prepared and testing is currently ongoing.
So where will we be next month/year? With more than 400 confirmed cases per 100,000 people for the last 14 days, Ireland has one of the highest numbers of Covid-19 cases globally, 10 times more than Germany and five times more than Sweden. Despite the liberal easing of restrictions, the case numbers are very high but declining in the UK, yet their vaccine uptake now lags behind ours. With only 72 per cent of adults fully vaccinated, it has been estimated that more than 93 per cent of adults in the UK have antibodies to SARS-CoV-2, suggesting that there is very high level of immunity in the entire adult population, induced by previous infection as well as vaccination. Recent studies have shown that infection with SARS-CoV-2 confers protection against reinfection which can persist for at least a year, especially against the same variant that caused the original infection.
This may add some credibility to the argument that lockdowns are not the solution to containing a pandemic, especially in the younger population, and may instead delay the generation of population immunity. However, the decision to vaccinate 12-15-year-olds in Ireland is a prudent one. Opening secondary schools before children are fully vaccinated is likely to result in substantial numbers of cases, with potential for closures of affected schools.
It has been argued that children under 12 need not be vaccinated because Covid-19 is a mild disease in this age group. However, since the start of the pandemic more than 300 children (0-15 years) have been hospitalised with Covid-19 in Ireland and, in the last two weeks, 2,551 cases of Covid-19 (12 per cent of all cases) were in 12-year-olds and younger. A recent study in the UK reported that about 4 per cent of children suffer symptoms that persist for at least four weeks and 2 per cent have symptoms that persist for longer than two months. It is also important to note that reaching population immunity against the Delta and other newly-emerging variants will be virtually impossible unless more than 85-90 per cent of the entire population is vaccinated.
A recent opinion piece in the prestigious science journal Nature suggested that Covid-19 is set to “become a disease of the unvaccinated, who are predominantly young”.
The good news is that the vaccine manufacturers have the capability of adapting the vaccines to deal with the changing dynamics of the virus
If our authorities make the right decisions regarding booster immunisation, and if the public continues its commitment to the vaccination programme, Ireland should be in a better place in the coming months. The challenge is to remain focused on knowing that, while the vaccines are highly effective at preventing severe Covid-19 leading to hospitalisation, they are less effective at preventing mild to moderate infection and virus transmission. The latter is key to reaching population immunity. Therefore mask-wearing and social distancing are likely to continue for some time.
This optimistic outlook for Ireland and other developed countries with high vaccine uptake does not reflect the future for many countries in Africa, South America and southeast Asia, which are currently suffering the highest number of cases since the pandemic began. In the absence of substantial numbers of additional vaccines being made available to these areas, the pandemic is set to continue.
The unchecked spread of the virus globally will facilitate the emergence of further variants of concern and their inevitable global spread. Effective and enforceable restrictions on travel from high-risk countries will still be required to minimise threats from imported variants.
However, the good news is that the vaccine manufacturers have the capability of adapting the vaccines to deal with the changing dynamics of the virus. This is especially true of the mRNA vaccines, which are very flexible and relatively straightforward to manufacture. Furthermore, a number of Indian vaccine manufactures have the capacity to make billions of doses of vaccines and they need to be resourced by richer counties to do so.
Analogous to the situation with influenza, Covid-19 is likely to become another infectious disease that requires annual vaccination to prevent infection with the latest variants. We are getting close to this in developed countries, but it will take some time before we see full control of the pandemic globally.
Kingston Mills is professor of experimental immunology and academic director of the Trinity Biomedical Sciences Institute at TCD