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Wednesday 29 November 2023 Dublin: 4°C
Sam Boal

Immunologist says boosters must be used 'at the right time' to protect against winter Covid wave

Professor Christine Loscher told The Journal that there needs to be a “coordinated response” to deal with future waves of the virus.

AN IMMUNOLOGY EXPERT has said that she has concerns about what a winter surge of Covid-19 might look like, and that new booster vaccines against the Omicron variant need to be timed so that they give the highest level of protection possible.

Covid-19 cases have been on the rise in recent weeks due to the spread of the BA.4 and BA.5 subvariants of the Omicron strain, which are replacing the previously dominant BA.2 variant, which spread across Ireland in late 2021.

According to the latest Health Protection Surveillance Centre (HPSC) report, there were 12,795 cases of Covid-19 reported between 26 June and 2 July, an increase of 22.6% compared to two weeks ago, when there were 10,435 confirmed Covid-19 cases notified.

As of Friday, there were 905 people in hospital with Covid-19, an increase from 685 two weeks ago. 35 people were in intensive care with the virus.

The seven-day positivity rate – the number of people testing positive out of the overall number of official PCR tests carried out – currently stands at 38.1%, an increase from 31.7% two weeks ago.

Speaking to The Journal, Professor of Immunology at DCU Christine Loscher said that we are “maybe a week away” from this wave’s peak.

“The positivity rate is starting to plateau out a little bit now, so that’s a good indication that we’re coming to the top of the peak. If you look at the pattern that was in Portugal, they climbed for five or six weeks and then started to decline, so that would kind of match what’s happened with us over the last four or five weeks,” she said.

This sentiment was echoed by Tánaiste Leo Varadkar during the week, when he told RTÉ’s Today with Claire Byrne programme that the current wave seems to be peaking “around now”, and that he expects the number of hospitalisations to start in the next two to three weeks.

He also said that he expects there will be an “extensive” Covid-19 vaccine campaign in the autumn ahead of a winter season that could see a further surge in cases of the virus.

“I’m more concerned about the next wave which will come in the winter, because that will happen when we’re indoors more and it might come at the same time as the flu. We haven’t had a serious flu season since 2019,” he said.

Loscher said that winter surges will always be more difficult to manage as the transmission rate will be higher due to people being indoors a lot more, as well as other viruses circulating around this time, such as the flu.

Winter wave

“This might make people a bit more susceptible. They might be immunocompromised because they already have something on board already, and you can pick up Covid when you have another infection.”

She said she would have concerns about what a winter surge is going to look like, given that we are now dealing with “much more transmissible variants than we were even coming into last winter”.

“We do need to be mindful that if BA.4 and BA.5 have been so good at causing infection, and if they are very immune evasive, which means they’re very good at avoiding your previous immunity from either infection or vaccination, if you transported into the wintertime and we have a wave like this, we could see much higher case numbers, and a bigger impact on workplaces,” she said.

I think everybody just knows so many people at the moment that have Covid and a lot of workplaces are really suffering from staff shortages. We’re seeing numbers still climbing going into hospital, and so the impact of a subvariant like BA.4 and BA.5 would definitely be a bit more apparent in the wintertime than it is at the moment.

However, while the variants are more transmissible, there is no clear evidence that they are more severe than previous variants.

According to Loscher, even if someone’s immunity is waning since their last vaccine against the virus, the T-cell immunity that they have built through previous vaccination and infection will prevent them from getting severely ill if infected with the new subvariants. 

“Even though BA.4 and BA.5 are circulating quite highly in the community and lots of people are getting Covid, we still have a lot of protection from the vaccines against severity,” she said.

She compared our immunity with that of Hong Kong, which recently experienced a severe surge of Omicron. Their population was poorly vaccinated – less than a quarter of people aged 80 and over in the city had been given two doses of a vaccine before the surge.

Their death rate following this surge was the highest seen for any variant at any stage of the pandemic. From January to March, 96% of deaths occurred in people aged 60 and older. Of those, 70% were unvaccinated.

“Omicron in a highly vaccinated population, like ourselves, where we have a lot of immunity built up over the last year and a half, we’re getting a lot of protection against severity. If you put Omicron into a very poorly vaccinated population, they don’t do as well,” Loscher added.

A second booster shot is currently being offered to people aged over 65 and people who are immunosuppressed, with the National Immunisation Advisory Committee (NIAC) currently considering whether people under 65 should also be invited to get a second booster shot of the Covid-19 vaccine.

LEO VARADKAR 2838 (1) Sasko Lazarov Tánaiste Leo Varadkar said he expects there will be an extensive Covid-19 vaccine campaign in the autumn. Sasko Lazarov

Varadkar said that while the Government will await the advice from NIAC in relation to this, he believes “that’s where it’s gonna go”. He also said that there will possibly be vaccines that are adapted specifically targeted to the Omicron variant.

Omicron boosters

Minister for Health Stephen Donnelly confirmed on Wednesday that NIAC are looking at additional boosters for those aged over 65 and under 65, as well as two new vaccines “that have been augmented specifically to deal with Omicron”.

Loscher said that an Omicron vaccine will help the body create antibodies that will be more effective against the current sub-variants.

“The difference between the spike protein in Omicron and the other original strain is that there’s a lot of mutations in the spike protein. So if you’re getting vaccinated and you’re making antibodies to the original spike protein in Covid-19, your antibodies just won’t be as good as they would be if you were vaccinating somebody against the Omicron specific variants.

You’ll make better antibodies. They’ll fit better, they bind better, and they’ll prevent the virus being able to cause an infection better. So really, it’s just the difference of what’s in the vaccine. The instructions for your body to make the antibody will be that they make an antibody that’s better against Omicron than against the previous variants that we had.

However, she warned that this needs to happen at the right time in order for it to be effective against a winter surge.

“Boosting now may be just boosting too early for that winter wave because we do know that the antibodies will wane and you’ll still get protection against severity, but if you want to boost a population in preparation for a wave, you want to boost them at the right time so that their antibody level is high enough to give them protection against getting the infection in the first place.

“If we’re going to give the same vaccine or an Omicron vaccine to the general population, we should be looking at doing that towards the end of August and start of September when you can start vaccinating people over the course of September and October.”

The Tánaiste also said that a winter surge may lead to the Government asking people to wear masks again in certain settings.

Coordinated response

Loscher believes that there needs to be a system in place where when we see Covid surging, everyone knows exactly what they need to do to minimise the risk, slow down transmission and prevent putting increased pressure on our healthcare system.

“My concern is the last two surges, this one and the last one, we’re not really seeing any kind of general public health guidance that we should be responding in any way, and I think that needs to be very clear,” she said.

She said that the response should always be the same – check that whatever vaccine you should be getting is up to date, wear a mask in crowded indoor settings, such as on public transport and in retail settings, and keep testing if you have symptoms. 

“I know we’re getting messages about boosters and vaccines over the age of 65, but there needs to be a very clear message that masks have a place in terms of protection at the moment, particularly well fitting, high-grade medical masks. I have noticed that there are a lot more people wearing masks now than there were even three weeks ago. Still very small numbers but definitely more, and they do have a role to play in reducing your risk.”

Going forward, Loscher said that surges every three or four months will probably continue for the time being until we learn more about the virus and have a long-term plan in place for how to deal with future waves.

The more we understand about the virus and the more we develop vaccines and antivirals, we’ll be better placed to know what the longer term strategy is. We know the vaccines are working really well against severity and deaths and hospitalisations. We know that they have a place and a use. When to use them, and predicting surges is what we will be able to do better over time.

“But I do think we’re going to be in these cycles of trying to figure out the best time to position the right vaccines, and being able to respond at the start of surges to minimise the impact.

“I think that we’ll get better at living with Covid. We’re living with it now, but I think we probably could live better with it, and I think that over time our strategy for how we deal with these surges into the future will just improve.”

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