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FactFind: Have Covid-19 vaccines been tested among older age groups?
Let’s take a look at how trials for the Moderna, Pfizer and AstraZeneca vaccines have involved older age groups.

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AS WE MOVE closer to the release of a vaccine for Covid-19, people are keen to know about how well the vaccines that have been developed work and the groups of people they have been tested on.

Some discussion has emerged in Ireland in recent days on whether vaccines, such as the ones from Moderna, Pfizer, and AstraZeneca, have been tested on groups of older people.

Speaking on Claire Byrne Live on RTÉ on Monday, 30 November, Professor Sam McConkey said that most people who enrol in vaccine trials are between the ages of 18 and 55.

McConkey, a specialist in infectious diseases at the Royal College of Surgeons Ireland (RCSI), said that “if we had a vaccine that was 100% effective at preventing death in the elderly, in people over 80, over 90, and in the vulnerable, and also to prevent transmission to other people that was widely available then that would be really good”.

“Unfortunately, in most Phase 3 trials, most of the people who enrol in them are young, healthy people between age 18 and 55, so probably these vaccines do work really well in preventing mild and moderate disease in young, healthy people age 18 to 55, but we know that that’s not really the group that really suffer death or severe illness from Covid-19,” McConkey said.

Several vaccines have now undergone the three key phases of clinical trials and are looking towards distributing them around the world. During clinical trials, a number of factors are investigated, including:

  • how well the vaccine protects against infection
  • the best dosage
  • any side effects

Let’s take a look at three of the frontrunner vaccines from Moderna, Pfizer, and AstraZeneca and to what extent their clinical studies included people from older age groups.


Moderna’s vaccine – mRNA-1273 – began its Phase 3 clinical trial in July, which involved 30,000 adults at research sites in the United States.

Early results from the clinical trial found that the vaccine, which Moderna hopes to have 20 million doses of ready by the end of 2020 to ship in the US, was shown to be 94.5% effective.

The vaccine uses messenger RNA (mRNA), which means the immune system is not exposed to the actual virus itself, but still triggers the production of antibodies in the immune system.

Moderna is currently filing for authorisation of the vaccine from the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA).

Eligibility requirements in the trial included the need for participants to be age 18 or over and to have not previously participated in a Covid-19 vaccine or treatment study.

Applicants needed to be healthy with no previous history of Covid-19, and if they had any pre-existing medical conditions, their conditions needed to be stable at the time of screening.

The study looked for participants who were at a high risk of Covid-19 infection due to their locations or circumstances, or at risk of severe Covid-19 due to being over the age of 65 or having an underlying medical condition.

Moderna eligibility requirements Moderna Moderna

Moderna / YouTube

Over 7,000 people over the age of 65 were participants in Phase 3 of Moderna’s clinical trial. Among the participants in Moderna’s vaccine Phase 3 trial:

  • 29% were between the ages of 25 and 44
  • 39% were between the ages of 45 and 64
  • and 25% were over the age of 65.

By comparison, according to the United Nations’ Department of Economic and Social Affairs, 9.3% of the world’s global population is over the age of 65.

This varies between regions – in high-income countries, 18.4% of the population are over 65, 8.2% in middle-income countries, and 3.3% in low-income countries.

Pfizer and BioNTech

The UK has formally approved the vaccine developed by Pfizer and BioNTech, which has been authorised by the UK’s Medicines and Healthcare Products Regulatory Authority (MHRA) for emergency use.

The Pfizer vaccine has been shown to be 95% effective with no serious side effects in its clinical trials and has passed its safety checks.

Pfizer and BioNTech have said that they are planning to produce up to 50 million vaccines globally in 2020 and up to 1.3 billion in 2021.

In a statement, the UK’s Department of Health and Social Care said that after months of “rigorous” clinical trials and data analysis, the MHRA “concluded that the vaccine has met its strict standards of safety, quality and effectiveness”. 

“The Joint Committee on Vaccinations and Immunisations (JCVI) will shortly publish its final advice for the priority groups to receive the vaccine, including care home residents, health and care staff, the elderly and the clinically extremely vulnerable,” the department said. 

It is expected that the vaccine will be available in the UK from next week.

The recent clinical trial of the vaccine enrolled 43,931 participants, of whom 42,722 have received the second of two vaccines.

The vaccine was studied at 150 clinical trial sites in the US, Germany, Turkey, South Africa, Brazil, and Argentina. Across the sites on an international level, 41% of participants are between the ages of 56 and 85.

In the US, 45% of participants are in the same age bracket. 

The efficacy of the vaccine was “consistent across age, gender, race and ethnicity demographics”.

The study observed efficacy of over 94% in adults over the age of 65.

AstraZeneca (Oxford)

The AstraZeneca vaccine developed at the University of Oxford has been clinically tested under two different dosing regimens.

The first regimen tested, which involved a halved first dose and a standard second dose, was found to have 90% efficacy.

The second dosing regime, which administered two full doses, had 62% efficacy.

In a study on the safety and immunogenicity (ability to provoke an immune response) of the vaccine during the second phase of trials that involved 560 participants:

  • 160 were between the ages of 18 and 55
  • 160 were between the ages of 56 and 69
  • and 240 were age 70 or over.

Adverse reactions to the vaccine decreased as age increased, with fewer adverse events reported in the older age groups than among 18 to 55-year-olds.

The study found that antibody reactions in the two older age groups “were comparable to those seen in younger adults”.

“Similarly, after a second dose of the vaccine, antibody levels increased, and this was also consistent for the older age groups.”

The study notes that “further assessment of the efficacy of this vaccine warranted in all age groups and individuals with comorbidities” and that more consideration in particular is warranted for those living in residential care settings or over the age of 80.

“Larger studies are now underway to assess immunogenicity, safety, and efficacy in older adults with a wider range of comorbidities.”

In the most recent clinical trials of the vaccine, which enrolled 24,000 participants from the UK, Brazil, and South Africa, the University of Oxford has said that the interim Phase III data “builds on Oxford’s phase I/II peer-reviewed trial results which have shown that the vaccine induces strong antibody and T cell immune responses across all age groups, including older adults, and has a good safety profile”.

In essence, Covid-19 vaccines such as those from Moderna, Pfizer, and AstraZeneca have been tested among older age groups, and older people have comprised sizeable proportions in each vaccine’s clinical trials.

For the two for which data has been shared – Pfizer and AstraZeneca – the efficacy of the vaccines among older people has been in line with the results on a broader scale. Ongoing studies into the vaccines are continuing.

The next stage of clinical testing – Phase Four – will involve following up with participants in the coming years.’s FactCheck is a signatory to the International Fact-Checking Network’s Code of Principles. You can read it here. For information on how FactCheck works, what the verdicts mean, and how you can take part, check out our Reader’s Guide here. You can read about the team of editors and reporters who work on the factchecks here.

applicants needed to be healthy with no previous history of Covid-19, and if they had pre-existing medical conditions, their conditions needed to be stable