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Thursday 8 June 2023 Dublin: 14°C
Sasko Lazarov People queueing to receive a Covid-19 booster vaccine earlier this week at the Croke Park vaccination centre in Dublin.
# Vaccines
Reader Q&A: Your questions on Covid-19 vaccine boosters answered
The Covid-19 booster vaccine rollout is ongoing in Ireland at the moment.

MORE AND MORE people around the country are receiving their vaccine booster doses to give enhanced protection against Covid-19 at the moment. 

Earlier this week, we asked readers to send in their questions about the booster rollout and any other booster jab queries. 

We received dozens of questions from readers asking when they can get their booster vaccine, whether it matters that they receive a different one to their original dosage and other confusion about the rollout so far. 

Here, we’ve done our best to answer your questions and concerns. 

Let’s start with an overall rundown on boosters, as many of the questions were focused on how long they take to become effective, timelines for when to get them and what exactly they do. 

  • What are booster vaccines?

A booster is an additional dose of a Covid-19 jab given after a person has received two Covid vaccine doses or the one-shot Janssen.

A booster dose has been shown to offer better protection to people vaccinated against Covid-19 if administered a number of months after their original vaccine course.

As with any vaccine, protection against illness can weaken over time. The HSE has said that people who received the Pfizer, Moderna or AstraZeneca jabs need to wait at least five months since their last dose before receiving a booster. 

People who received the Janssen (Johnson & Johnson) one-shot jab are advised to wait at least three months before getting a booster dose, the HSE said.

People who had Covid-19 since they were vaccinated can get a booster at least six months after their positive test result.

The booster jabs being used in Ireland at the moment are the mRNA vaccines from Pfizer and Moderna. So regardless of the original vaccine you received, you will be offered a Pfizer or Moderna booster jab.

These are shown to be effective at improving the immunity your body has against Covid-19. A full dose of Pfizer or a half dose of Moderna is used as a booster jab dose. 

However, under 30s are not being offered the Moderna jab as a booster at the moment while evidence is being assessed around this vaccine leading to some rare instances of an inflammation of the heart in men aged 16-29.

This is a precautionary measure and experts have said more evidence is needed around it. 

Pfizer doses account for the vast majority of boosters in Ireland. In total, almost 880,000 booster doses have been administered so far, according to the latest data.

  • Who is eligible at the moment?

The National Immunisation Advisory Committee (NIAC) has advised that people at highest risk of severe Covid-19 breakthrough infection, such as older people and those with underlying conditions, should be prioritised for booster jabs. 

Boosters are currently being offered to:

  • People aged 60 or older
  • People aged 16 to 59 with an underlying health condition 
  • People living in a nursing home or a long-term healthcare facility
  • Healthcare workers

The HSE said that anyone aged 70 or older who has not yet received a booster dose will be invited to do so by a GP. 

People will either receive a booster appointment from the HSE directly, through their GP or by contacting participating pharmacies. 

The HSE said that anyone who has already received a booster dose who then gets an appointment text from the health service should reply to the text with the word ‘REJECT’. 

Walk-in booster vaccination centres are also open for specific groups of people on certain days. Anyone who is in the currently eligible categories can show up to these clinics when they are being held for their specific cohort to receive a booster.

Large queues gathered at these clinics in Citywest and Croke Park in Dublin at the weekend with the HSE apologising for the lengthy wait times experienced by some people in attendance. You can find details on upcoming walk-in centres here

Those aged 50 to 59 are listed by the HSE as being next in line for boosters, with jabs due to start for this cohort in mid-December.

The order after that is: 

  • All pregnant women aged 16 or older
  • Everyone aged 40-49 
  • Everyone aged 16-39

NIAC set out in its most recent recommendation that for those aged 16-39, boosters should be administered in descending order of age cohort – 30-39 years, 20-29 years and 16-19 years.

But for people aged 16-29 who received the Janssen vaccine, NIAC recommended that they be offered a booster dose in parallel with people aged 30-39 who received other vaccines.  

In response to queries from The Journal, a spokesperson for the HSE said the health service is “currently planning” to operationalise these recent recommendations from NIAC “in a safe and timely manner”. 

“When it is time for your vaccination you will get a text message from the HSE with a vaccination centre appointment,” the spokesperson said. 

  • Will those of us who received the Johnson & Johnson vaccine be prioritised in any way for a booster?
  • ‘I am 55 and received the Janssen vaccine in May. When can I receive my booster?’

We received several versions of this question from people who received the Janssen vaccine more than three months ago.  

Around 236,000 J&J vaccines were administered in total in Ireland. One-third of these were given to people aged 50 to 59 and two-thirds to those aged 18 to 49. 

Tánaiste Leo Varadkar told RTÉ radio recently that he had “profound concern” for people who received the J&J vaccine and that he hoped to have a positive decision on this group receiving an mRNA dose soon. 

Essentially, protection from the Janssen vaccine appears to wane quicker compared to two-dose vaccines. The J&J stopped being used by the HSE in recent months when mRNA vaccine supplies were more consistent.  

In September, J&J published research showing that their jab was 81% effective at protecting against hospitalisation and 79% against infection. 

It found that a booster jab given two months after the initial dose provided higher levels of protection against severe illness. 

However, other studies have found that the efficacy of the vaccine’s protection against infection and severe illness wanes over time. 

In its most recent recommendations, NIAC referenced a population-based study in Puerto Rico which showed that vaccine efficacy declined to as low as 30% for Janssen over time.

NIAC said that waning immunity – which is a feature of all Covid-19 vaccines – combined with the initial lower efficacy of the one-shot vaccine compared to other jabs “may make recipients more susceptible to breakthrough infections”. 

NIAC also said that because of this, “offering an earlier booster vaccine” to people who received the J&J “may help to control the surge in case numbers in younger people whose lifestyle, work and living conditions may increase their social mixing”. 

As outlined earlier in this article, NIAC has advised that younger cohorts who received the J&J dose can be prioritised over their peers who received mRNA jabs as the booster campaign continues in the new year. The HSE said it is currently working on this and other recommendations from NIAC around boosters.

However, at the moment people with the Janssen vaccine aren’t being prioritised to receive a booster unless they are in the other eligible groups such as over 60s or healthcare workers.

  • ‘Why do we need booster vaccines and what do they offer?’

In short, they help keep us better protected against Covid-19. Protection from vaccines reduces over time so getting another dose of a Covid vaccine helps bump up your protection against infection, transmissibility and serious illness.

This increased protection is already being seen among older age groups after receiving a booster dose. 

Speaking on Wednesday, Professor Philip Nolan from NPHET said: “We’re beginning to see the effects of booster vaccination in terms of incidence in 70 to 79 year olds now. So it was over 80s, now it’s over 70s you’re beginning to see the effects.

“In terms of hospitalisation, we’re down to about 15 hospitalisations per 1,000 cases at the moment, that was 20.

“It’s unlikely to go much lower, and that effect is particularly marked in the over 70s where yes, you’re beginning to see not only a reduction in incidence but a reduction in the proportion of cases that are requiring hospitalisation.” 

The Chief Operations Officer of the HSE Dr Colm Henry said breakthrough infections of people who have received a booster vaccine haven’t yet been seen in Ireland but said it will “probably” happen down the line. 

“We’ve known breakthrough infections have always happened… the greater number of cases out there in the community, the greater amount of community transmission, the greater the likelihood is that you’ll see breakthrough transmission,” Dr Henry said at a HSE briefing. 

He said the overall figures from Israel, where booster vaccinations have been ongoing for several months, show a “huge drop in serious illness, hospitalisation in those who received the booster vaccine”. 

  • Is there a difference between a booster dose and an immunosuppressed dose?

Yes. People who have a weak immune system may have already been offered an additional Covid-19 vaccine dose to give them better protection against Covid-19. 

Covid vaccines can be less effective in people who are immunosuppressed or immunocompromised, leaving them at greater risk of becoming severely ill if they contract Covid-19. 

Speaking on The Journal’s The Explainer podcast last week, DCU professor of immunology Christine Loscher explained the difference between booster doses being given to the general population at the moment and additional doses already administered to people who have weak immune systems.

“A booster is given to somebody who had a normal immune response, doesn’t have any immunocompromised condition, and they have waning immunity after a period of time, maybe up to six months. And then they’re given a booster to boost that immunity,” she said. 

“People who are immunocompromised don’t normally have a very powerful immune response to a vaccine in general.

So the data is kind of showing that the response that they might have had after the first and second dose might not be as powerful as other peoples’ and therefore the additional dose is just part now of their vaccine regime to give them as much protection as possible.

“They may also have boosters in the future if their immunity starts to wane, but their additional dose really is to give them the best possible chance of having as high an immune response as possible to the vaccine.”

The HSE has said that people who are immunocompromised who have already received their third additional vaccine dose don’t need to receive a booster dose at this time. 

The HSE also clarified that the additional dose does not count as a booster dose. 

“The National Immunisation Advisory Committee has not recommended a Covid-19 booster vaccine for people who are immunocompromised and received/will receive an additional dose of the Covid-19 vaccine,” a HSE spokesperson said. 

  • How long does it take the booster to become effective?

The HSE said that clinical studies show boosters are very effective at preventing illness 1-2 weeks after they are administered. 

  • Can I receive a booster vaccine in Ireland if I was vaccinated in another country?

The HSE has said people who received their Covid vaccine in another country can avail of a booster in Ireland at the moment once they are eligible under the current prioritisation list.

A HSE spokesperson advised anyone in this situation to ring HSE Live on 1800 700 700 to register for a booster vaccine. They will be asked to give information in relation to the vaccine they already received such as the date and location they received it and the batch number. 

  • ‘I am pregnant and double vaccinated. Should I get the booster? How do I get it?’ 

Pregnant people are at no higher risk of contracting Covid-19, but people who get the disease are at higher risk of severe illness and adverse outcomes.

NIAC said pregnant people should therefore avail of a booster vaccination “at the earliest opportunity”. This advice was similar during the original vaccination campaign when women were encouraged to get vaccinated during pregnancy to minimise their risks if they become ill. 

The HSE said booster doses will soon be offered to pregnant people in Ireland. 

Anyone who is pregnant and a healthcare worker or has an underlying condition can get a booster jab now if it has been the sufficient amount of time since their last vaccine dose. 

  • Is it safe to get a different vaccine than my original vaccine I received earlier this year? 
  • ‘I’m young and received the J&J vaccine. I want to check my antibody levels as I feel bad taking a booster shot when my time comes given people in developing countries are still waiting for vaccine doses. I am also not very keen on the idea of needing another vaccine dose when we don’t know the long-term effects.’ 
  • Is it okay to mix and match different vaccines? What has the EMA said? 

NIAC has said that booster doses of mRNA vaccines on top of the Covid vaccines people have already received hasn’t shown “any unexpected short term safety concerns”. 

There has been commentary around the booster dosage campaign that perhaps the Covid-19 vaccines will end up being three-dose schedules since boosters are shown to have such impactful responses to immunity. 

Speaking on The Explainer podcast, professor Christine Loscher from DCU said it’s “really difficult when you’re trying to manage a new vaccine regime” to determine the dosage needed over time. 

“When we look at Covid, because it’s such a new vaccine, we really had to wait and see whether or not waning immunity would matter as much as it does,” she said. 

I don’t think we would be as worried about boosters as we are if we weren’t dealing with Delta.

“I think because it’s so transmissible and because we’re in winter, it’s posing more of a problem for our case numbers and that’s why the wanig immunity is more of an issue.” 

She added that data from the Israel booster vaccine rollout showed “it really looks like this third dose, this boost is really giving a much more enhanced level of immunity than we ever would have had before”.

“The more you’re exposed in terms of vaccines and boosters, the more higher quality your antibody is, so it’s not just that there’s more antibody there, it’s actually more specific and it works better.”

Essentially, the booster offers you better protection against the disease a few months after receiving your initial vaccine doses. 

NIAC recommended in August that vaccine types can be mixed in certain circumstances. This meant, for example, that people who received their first dose of AstraZeneca could receive an mRNA vaccine from Pfizer or Moderna for the second jab. 

This was recommended for three main reasons – to increase flexibility of vaccine delivery, to minimise the rare risks associated with younger age groups receiving viral vector vaccines (AstraZeneca or J&J) and to increase protection against variants of concern. 

The European Medicines Agency (EMA) said that booster doses can be considered at least six months after the second dose of a Covid-19 vaccine for people aged 18 and older. The advice from NIAC and the HSE is a gap of at least five months. 

The EMA has said there are “good scientific grounds” to expect the approach to mix different vaccine types to be safe and effective but it has not yet made a definitive recommendation on the practice despite it being common in many countries. 

DCU’s professor Loscher said the available evidence around mixed vaccines for booster jabs showed show that “not only is it bringing the immunity level up, but actually you’re getting a much more enhanced response”.

She said people who may have felt they were less protected with AstraZeneca “get that bonus now of that mixed booster” with an mRNA dose to give enhanced immunity.

“Really we think the reason for that is, is that both of those vaccines actually deliver the information about what the body needs to do in terms of mounting this immune response, they deliver it in two different ways,” she said, on how mRNA and viral vector vaccines work differently.

“And sometimes, that makes for a higher quality, more enhanced immune response. And that’s really what we’re seeing very strongly coming through with those mixed vaccine regimes.”

As for the concerns about developing countries not having as much access to vaccines, this issue has been criticised by the World Health Organization among other groups throughout the pandemic. 

In September, WHO chief Tedros Adhanom Ghebreyesus Tedros called on countries to avoid giving out extra Covid jabs until the end of the year, pointing to the millions worldwide who have yet to receive a single dose.

“I will not stay silent when the companies and countries that control the global supply of vaccines think the world’s poor should be satisfied with leftovers,” he said.

“We do not want to see widespread use of boosters for healthy people who are fully vaccinated.”

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