Updated:19/11/2020 08: 00h
After the announcement of the positive results of the vaccines for Covid-19 from Pfizer and Moderna, today they are published in the prestigious magazine «The Lancet» phase 2 vaccine data Oxford University Y AstraZeneca. They are very hopeful: the vaccine is safe and elicits an immune response in healthy older people. It is precisely this group that has a disproportionate risk of developing a serious illness from Covid-19, so it is essential that any vaccine be effective in this group.
The study, carried out 560 healthy adults, including 240 70-year-olds, shows that the vaccinea is better tolerated in older people compared to younger adults and produces a similar immune response in both age groups.
The authors note that their findings could be encouraging if the immune responses found in their study are associated with protection against coronavirus infection, but this trial did not assess efficacy and phase 3 trials are ongoing to confirm this.
Researchers have seen that the vaccine induces immune responses in both parts of the immune system in all age groups and at low and standard doses. Thus, it generates a T cell response within 14 days after to the first dose of vaccination (cellular response), and an antibody response within 28 days of the booster dose of the vaccine (humoral). [Una respuesta celular podría identificar y atacar células infectadas con el virus y la humoral detectaría y destruiría al virus cuando circule en la sangre o en el sistema linfático].
Phase 3 trials They are underway to confirm these results – as well as the efficacy of the vaccine – to protect against infection in a broader panoply of people, including older people with previous pathologies.
The lead author of the study, Andrew Pollard, from University of Oxford (UK), ensures that, “sometimes, immune responses to vaccines are worse in older people because the immune system gradually deteriorates with age, which also makes them more susceptible to infections.” Therefore, he insists, “it is crucial that Covid-19 vaccines are tested in this group, which is also a priority for immunization.”
In this sense, Maheshi Ramasamy, of the Oxford University, notes that the robust antibody and T-cell responses seen in the older people in the study are encouraging. “Populations most at risk of severe illness from Covid-19 include people with previous pathologies and the elderly. We hope this means that our vaccine will help protect some of the most vulnerable people in society, although more research will be needed before we are sure.
The new study is the fifth published clinical trial of a SARS-CoV-2 vaccine tested in a population of older people. It is true that other Covid-19 vaccines generate immune responses in this group, it is difficult to compare the results between different investigations.
For example, a study with the vaccine MRNA from Modern showed similar immune responses in the young and the elderly, while other trials, conducted with the vaccine CanSino single dose of Pfizer / BioNTech, and of SinoPharmm indicate lower responses in older people.
This trial divided the 560 participants – 160 aged 18 to 55, 160 aged 56 to 69, and 240 aged 70 and over – into 10 groups. All received either the standard or low dose vaccine or a control vaccine – the meningococcal conjugate vaccine.
Those older than 55 years were also divided into groups and received one or two doses 28 days apart. The study includes only healthy participants and not those with comorbidities.
Before receiving the vaccine, all participants had a blood test to determine if they had previously been infected with SARS-CoV-2. Those who had antibodies were excluded.
The vaccine showed an immunogenicity similar in all age groups after a booster dose. It induced antibodies against the SARS-CoV-2 spike protein and receptor-binding domain 28 days after a single low or standard dose in all age groups. After the booster dose, antibody levels increased on trial day 56, regardless of the dose or age of the participant. The same was observed with neutralizing antibody levels on day 42, two weeks after the booster dose of the vaccine. At 14 days after the booster dose, 208 of 209 (more than 99%) of the participants had neutralizing antibody responses.
The World Health Organization (WHO) has outlined a series of criteria for Covid-19 vaccines: they must be aimed at the highest risk groups, such as the elderly, as well as being safe and effective in preventing disease and / or transmission, and providing at least six months of protection for people frequently exposed to the virus, such as healthcare workers.
«Our study – argues professor Sarah Gilbert– answers some of these questions about the protection of the elderly, but leaves others unanswered about the effectiveness and duration of protection ».
Researchers know that the results must be confirmed in older people with previous pathologies to ensure that the vaccine protects those who are most at risk of contracting the severe disease Covid-19.
Regarding adverse effects, most were mild: pain and tenderness at the injection site, fatigue, headache, fever, and muscle pain; but they were less frequent in the elderly than in the younger ones.
However, the authors acknowledge some limitations in their study, including the fact that the participants in the oldest age group had a mean age of 73 to 74 years and few previous pathologies, so they may not be representative of the older population. in general, including those who live in residences or those over 80 years of age. In addition, they note that almost all the participants were white and non-smokers. The phase 3 trial is included people of diverse origins, countries and ethnicities.
“It is encouraging that more studies are being done in populations of older people who are anxiously awaiting a safe and effective vaccine,” he said. Melissa Andrew, Delhoise University from (Canada), which did not participate in the study.