Dr Kevin McCarroll
Medical Matters
The approval of the Pfizer/BioNTech vaccine by British authorities early this month truly marks a great triumph for science and not just in the battle against Covid-19. Scarcely could anyone have imagined that at the start of the year the hopes of the world would rest on the approval of a vaccine for the worst global pandemic in over a century. With over 2000 deaths from Covid-19 in Ireland and the hardships and toils suffered over the last year, it’s most welcome news this Christmas.
The level of protection provided is about 95% and there were no significant side effects in over 43,000 people vaccinated”
For the first time, this vaccine uses technology never applied before in that no actual virus is needed for its production. In short, part of the genetic code (mRNA) from the SARS-CoV-2 virus that encodes its spike protein can be manufactured meaning the rate at which the vaccine can be made is dramatically accelerated. Consequently, mRNA vaccines may offer a more rapid solution to new viral outbreaks in the future. Another important advantage is that they should be easy to modify in the event of viral mutations.
The Pfizer/BioNTech vaccine requires two doses administered three weeks apart with full immunity likely to develop about seven days after the second shot – meaning it takes about one month for full effects. Importantly, data shows it also works well in older people. The level of protection provided is about 95% and there were no significant side effects in over 43,000 people vaccinated. The company will however continue to monitor study participants for any adverse reactions over the next two years .
In practise when the vaccine is rolled out to millions of people there is a very small risk that rare side effects may emerge. But there is no reason to believe that this is any more likely to happen with this or other Covid vaccines. Indeed, the risk of any major adverse effects with any vaccine is extremely low. The government though has agreed to indemnify five of the pharmaceutical companies producing the vaccines in the event of any liabilities arising from complications.
The Moderna vaccine using the same technology is also 95% effective and appears to provide 100% protection against severe Covid. The Oxford vaccine is up to 90% effective too depending on the dosing regime used, but cost is much lower and it can be kept in a standard fridge.
The US Food and Drug Administration (FDA) has been slower to analyse the vaccine trials but this was in part because they waited until all the information became available unlike in the UK where the data had been looked at from an earlier stage as it came in.
However, the mass vaccination of the majority of the population will be a logistical challenge made harder by the need for two jabs”
Vaccine uptake of course is crucial with about 70% of the population needing to be immunised to provide ‘herd immunity’. Whether the vaccine actually stops people becoming infected with the virus as opposed to preventing Covid symptoms is unclear. But ultimately if not having symptoms one’s infectivity is likely to be less and so spread also curtailed. However, recent surveys suggest that about 40% of Irish people are reluctant about being vaccinated so reassurance will be important.
The Pfizer vaccine can be stored in a standard fridge for a few days after thawing while with the Moderna vaccine this can be extended for up to 30 days, making distribution to nursing homes, vaccination centres and even GP practises easier. However, the mass vaccination of the majority of the population will be a logistical challenge made harder by the need for two jabs.
And so, who should be vaccinated first? The most vulnerable and those in nursing homes should be the priority along with carers for older people. After that healthcare workers and other older adults and those with respiratory, cardiac and other long-term conditions.
But how long will immunity last? We simply don’t know the answer. We know that seasonal coronviruses that cause common colds provoke immunity that can last for up to one year but then wanes off. There are also rare reports of SARS-CoV-2 re-infection. For this reason, even those who have suffered with Covid-19 will be vaccinated. However, other vaccines are known to give longer immunity than is sometimes acquired with natural infection. It is very likely that there will be some cases of Covid-19 well into the end of next year and even after, given that no vaccine is 100% effective and the virus’ high infectivity. However, vaccination can eliminate nearly all of the severe cases and effectively reduce spread.
But we are going to have to wait until January in the Republic for the vaccination programme to start. In the meantime, given the ease in restrictions, there will undoubtedly be an increase in Covid-19 cases after Christmas. Not surprisingly, the CSO estimates that one in five people admit they are ‘very unlikely’ or ‘unlikely’ to comply with restrictions that would prevent them seeing family and friends over the holiday. Hopefully by Spring of next year, Covid numbers will be low and a semblance of normal life will have returned.
