Cases of Covid-19 in Ireland have been rising in recent weeks as a spike in infections over the coming months is expected.
After infection, you may have developed some immunity to the virus, but just how long does it last?
Dr Cillian de Gascun, Director of the National Virus Reference Laboratory, told RTE Radio One why we are seeing a rise in Covid cases and how long protection lasts for those who have already been infected.
He said: “I think the primary reason we are seeing it is we have a new variant circulating against which we don’t have full immunity in the population.
“So people will have heard a lot about Omicron BA.4 and BA.5 and certainly looking at our own data it would appear that they account for more than 90% of our cases at the moment and the problem with BA.4 and BA.5 and the reason we group them together is because they share the exact same spike protein and obviously people will be familiar with the spike protein at this stage. It’s the part of the virus that the virus uses to get into our cells to cause infection, and it’s also the part of the virus that is included in the vaccines that we have available, and the difficulty with BA.4 and BA.5 is that they’re sufficiently different from Omicron BA.1 which is what caused our very large spike over December and January.
“The problem is people who were infected with Omicron BA.1 don’t have protection from that infection against BA.4 and BA.5.”
“Similarly, people who would have been infected with Omicron BA.2, which peaked here in the second half of March, they will have some level of protection against BA.4 and BA.5, but it’s not complete.”
Dr de Gascun explained that initially, the immunity gained from infection was thought to last a lot longer, but this is now not the case.
He said: “If we go back to 2020 when this started, it looked like natural immunity against reinfection potentially would have lasted maybe six, nine, twelve months, against if you were infected or reinfected with the same variant or the same virus.
“Unfortunately, what we’ve seen over the two years since is that new variants have emerged the actually duration of immunity is actually quite short more in the region of four to six months maybe even less.”
He added: “We are seeing some evidence that would suggest that the durability of protection against or following Omicron infection is maybe even shorter than previous variants such as Alpha or Delta.
“The reason for that, and again people might remember this, that Alpha and Delta were viruses that were capable of infecting the lungs causing quite severe disease, and I suppose one of the benefits to a degree of Omicron even though it can cause severe disease in an unvaccinated population it was more likely to cause infection in the upper airways and less likely to cause severe disease despite the fact that it was far more transmissible.
“So actually, the virus, if you like, had sort of sacrificed some of its severity in respects for transmissibility.
“So the good news about BA.4 and BA.5 is that they’re very much Omicron like we’re not going back to the more severe viruses like alpha and delta, but at the same time, it’s probably more transmissible again than Omicron BA.1.”
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