Q&A: Do I need a second booster shot given the rising cases of Covid-19?

It’s been a while since I got my Covid-19 booster. Given the amount of virus that’s around at the moment, do I need another booster?

This is a question that is on the mind of a lot of people at the moment. Cases are rising and so is the number of people in hospital with Covid, so the threat posed by the disease hasn’t gone away. The illness caused by the Omicron variant is generally less severe than in previous waves, and only half of those in hospital are there because of Covid as opposed to other medical problems. But waning vaccine immunity is thought to be one of the factors behind the increase in cases and serious illness.

In one US study, for example, the effectiveness of the Pfizer booster against hospitalisation declined from 91 per cent to 78 per cent in four months up to last January.

That’s concerning. It sounds like we need a fourth dose.

Regulators on both sides of the Atlantic are considering the necessity for a fourth dose but the picture is not so simple. The protection from vaccines against infection does wane within months, but the protection against hospitalisation and death declines more slowly. Some studies suggest that three doses of a vaccine are enough to protection most people from serious illness for a long time. One reason is that specialised immune cells called T-cells produced after immunisation can provide long-lasting protection.

We already provide a fourth dose for immuno-compromised people, and there may be a case for giving one for older people, in whom protection seems to decline more quickly. But for the rest of us, there hasn't been sufficient reason up to now to recommend a fourth dose. Studies from Israel have suggested only marginal benefits from an additional booster.

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But what about the rise in cases?

Yes, that could change the calculus. With so many infections around, vulnerable people are clearly at risk. A rise in cases was inevitable after restrictions were lifted, but the current increase in shaping up to be a fresh wave across Europe. If yet more people end up in hospital due to Covid, that might convince regulator not to wait until the autumn to give the go-ahead for another booster.

What are the options if they do?

Moderna on Friday applied for emergency use authorisation in the US for a second booster for adults. Earlier in the week, Pfizer sought approval from US authorities for a second booster, but only for those aged 65 and over. The European Medicines Agency says there is not enough data to support the use of a second booster in the general population.

In Ireland, the National Immunisation Advisory Committee is unlikely to give the go-ahead to a second booster until the EMA changes its stance.

Even if Niac were to approve a second booster, the take-up is likely to be lower. While 95 per cent of adults were administered the primary vaccine course, most receiving two doses, only 70 per cent opt to receive a booster.

Niac’s most recent decision was to approve a booster for 12-15 year-olds but up to now demand has stayed very low in this age group.

The vaccine companies, which stand to make further profits from boosters, are also working on vaccines adapted to the Omicron variant. It is highly likely the general population will be advised to get boosted next autumn, but not before then.