People due to receive their Covid-19 booster vaccine in coming weeks will primarily be offered the Moderna dose at HSE vaccination centres.
The HSE is reported to have large supplies of Moderna due to expire next month, so that will be the main vaccine administered over coming weeks to the over-60s, over-50s, healthcare workers and younger people in vulnerable groups – though it will be restricted to people over 30.
Anecdotally there are indications some people may be reluctant to take the Moderna vaccine. This may be due to Irish stocks about to expire shortly and/or confusion about its efficacy. This follows the company’s chief executive Stéphane Bancel warning last week the Moderna jab may not be as effective against Omicron as it had been with the Delta variant.
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The HSE has confirmed recipients will have no choice on what vaccine they are given.
What type of coronavirus vaccine is the Moderna jab?
It is a new kind of synthetic “mRNA vaccine” – the Pfizer/BioNTech vaccine is from the same stable. They provide excellent protection against severe illness and hospitalisation – and have played a critical role in reducing Covid-19 deaths since being approved. A downside, however, is that they must be stored at very cold temperatures.
In a half-dozen studies published earlier this year the Moderna jab appears to be more protective over the long term than the Pfizer-BioNTech jab. Protection against symptomatic infection was 93.1 per cent for people aged 60 and above who originally received the Oxford/AstraZeneca jab and 94 per cent for BioNTech/Pfizer recipients a fortnight after the booster shot was administered.
Should people be worried about receiving a soon to be out-of-date vaccine?
In short no, as they retain the ability to boost antibody production within currently approved time spans – though inevitably potency wanes over time. The Pfizer, Moderna, AstraZeneca, and Janssen (Johnson&Johnson) vaccines were put on the market with emergency use authorisation of up to six months.
This compares with a shelf life of two to three years for most vaccines and other medicines. This is an "inevitable consequence of getting the vaccines out of the door as quickly as possible" , chief scientist at the Royal Pharmaceutical Society Gino Martini told the journal BMJ.
Months later,these “emergency” expiry dates remain in force for these vaccines. For approved Covid-19 vaccines, the initial shelf lives were based on data available at the time of submission for regulatory approval.
The long-term shelf life has not been extended for any of the vaccines. A shelf life extension would require supporting evidence from relevant stability studies. Vaccine manufacturers are monitoring batches of vaccines with the aim of providing a longer shelf life; probably the usual two years.
What about the Omicron threat?
While Moderna said existing vaccines including its mRNA version will probably be less effective against the Omicron variant, most experts believe they will continue to provide significant protection against severe disease and hospitalisation. It should be stressed, however, definitive indication has yet to emerge. That will be a matter of weeks, if not days.
Moderna has confirmed it is developing an Omicron-specific booster though manufacturing the new vaccine would take time. Tens of millions of doses could be available in the first quarter of 2022, but scale-up would not happen until the second quarter – provided it is shown such boosters are required.
What is the latest indication on the benefits of mixing vaccines?
Evidence supporting a mixing of vaccine doses has hardened over recent months. A study this week shows combining a first dose of the AstraZeneca Covid-19 vaccine with a second dose of either the Moderna or the Novavax jabs results in far higher levels of neutralising antibodies and T-cells compared with two doses of the AstraZeneca jab.
This finding also has important implications for lower-income countries that have not yet completed their primary vaccination campaigns as it suggests you do not need access to mRNA vaccines – and therefore ultra-cold storage facilities – to trigger an extremely potent Covid-19 vaccine response.
The study also bolsters confidence that using the Moderna vaccine as a booster dose in people who have previously received the AstraZeneca jab should result in high levels of neutralising antibodies and T-cells.
It follows separate data published last week suggesting the Pfizer and Moderna booster jabs can dramatically strengthen the body’s immune defences.
The National Immunisation Advisory Committee (Niac) has decided not to recommend the Moderna booster vaccine for eligible people aged under 30 years “as a precaution”. A similar approach has been taken by authorities in France and the Scandinavian countries after early data showed a higher rate of myocarditis in young males who received Moderna compared to those who were administered Pfizer.
For those aged 30 and over, Niac advises the Pfizer vaccine or a half-dose of Moderna should be administered after a six-month interval, though for operational reasons a minimum interval of five months may be used.
There are early indications the infection rate is slowing down among those aged 75-79 due to the administration of boosters. Covid-19 infections have already fallen among those aged 80 and over, where booster coverage is above 80 per cent. It also describes as encouraging a decrease in the number of infections among healthcare workers.
The rise rapid rise of Omicron elsewhere, which is likely to be replicated in Ireland soon, is the big new complicating factor. So all bets are off until clarity on the exact extent of that threat emerges.