Another maybe since I am not over 80.
An NIHR and UKRI funded study has found that people aged over 80 who received their second dose of the Pfizer–BioNTech mRNA vaccine after 12 weeks have significantly higher peak antibody levels than those who received it after 3 weeks.
The study is the world’s first comparison of the immune response in any age group between administering the second Pfizer COVID-19 vaccine dose at three and 12 week intervals.
Data from the preprint paper show that people aged over 80 who were given the second vaccine after 12 weeks had a three-and-a-half times greater antibody response compared to those who received it at three weeks.
The researchers also found peak T-Cell immune responses were lower after the delayed 12 week second vaccine. However this did not cause antibody levels to decline more quickly over the nine weeks following the booster shot - with responses comparable when measured at a similar time point following the first dose.
The team concluded that extending administration of the second Pfizer vaccine to 12 weeks potentially enhances and extends antibody immunity, which is believed to be important in virus neutralization and prevention of infection against COVID-19.
175 older people over 80 took part in the study - with 99 participants receiving the second vaccine at three weeks, and a further 73 participants receiving their second dose at 12 weeks.
Participants gave blood samples for lab analysis after their first vaccine and then two to three weeks after their second dose.
After their second vaccine, spike-specific antibodies were detected in all participants, irrespective of how far apart their doses were. However, after the second vaccine the average concentration of antibodies was 3.5 times higher in the 12-week interval group (4,030 U/ml) compared to the three-week interval group (1,138 U/ml).
In relation to the cellular (or T cell) immune response, which plays an important role in supporting and maintaining antibody production, the team found that within the three-week interval group, 60% had a confirmed cellular response at two to three weeks following the second vaccine - although this fell to only 15% eight to nine weeks later.
First author Dr Helen Parry, NIHR Academic Clinical Lecturer at the University of Birmingham, said:
“SARS-CoV-2 vaccines have been remarkably effective in providing large-scale protection against infection and symptomatic disease - but many questions remain regarding their optimal delivery for provision of effective and sustained immunity.
“This is the first time antibody and cellular responses have been studied when the second vaccine is given after an extended interval. Our study demonstrates that peak antibody responses after the second Pfizer vaccine are markedly enhanced in older people when this is delayed to 12 weeks.
“This research is crucial, particularly in older people, as immune responses to vaccination deteriorate with age. Understanding how to optimize COVID-19 vaccine schedules and maximize immune responses within this age group is vitally important.”
The study was supported by the UK Coronavirus Immunology Consortium and the British Society for Immunology.
Hm. Well, interesting. This (might) suggest that antibodies in older people can be boosted by delaying the second shot to 12 weeks from 3 weeks. A few caveats or questions spring to mind, though.
The first is, with millions and millions of people getting vaccinated, what were they doing only assessing 175 people? That is a tiny sample size. Small sample sizes can be skewed by things the population they used have in common, such as being middle-class with good health care, or being all of one general ethnic or geographic group. The results can't be said not to suggest anything, and they certainly point out fruitful paths for more research, but it seems that at this stage they don't prove anything. (Couldn't they find more than a handful of people over 80 to wait 12 weeks for their second shot? My parents would have volunteered!)
My guess would be that they limited this to people over 80 because people that age have less strong immune responses to vaccines overall, and are often given a stronger vaccine for that reason (for example, the flu shot). While it's nice to know that something could be done to boost effectiveness in this age group, if the people doing the assessment would explain why they didn't include younger people, it would help the average interested person to understand what they are saying. (It would be specially interesting to hear if they already knew there was no difference between 3 weeks and 12 weeks in that population.) It would be possible for a casual reader to hear about this research (especially if you only read headlines in the newspaper) as "Delay the second shot for a better immune reaction." But it might mean no such thing for younger people. And there is the risk of getting Covid in between the shots, which in people delaying the second shot would go from three weeks of exposure to what's out there, to 12 weeks of exposure to what's out there. If doing so for the reason of boosting future immunity, people should know if it would even help.
I'd like to see them use the results of this study to prompt further assessment of the question, "Of all people getting the vaccine, is waiting as long as 12 weeks for the second shot a good idea because it boosts antibody levels for anyone getting the shot?" If they find out that this result is generally applicable to people old and young, people could balance the risk of getting sick if they wait for their second shot, versus having a stronger antibody response. I'm sure such research will be forthcoming sooner or later, it's too bad it isn't here now. But this is a start, I guess.
Perhaps it was 175 because there wasn't much government money allotted to the trial. Depending on stability (in this case the age was set so if the measurement of antibodies and T cells is accurate ) you can get 95% confidence (fwiw) with small groups like this one - although I know nothing more than what I read about this kind of trial and 95% is only as good as the number of conditions that can affect it. Perhaps this was intended to be the first trial for these researchers and others who become interested in the results to try to figure how to do a larger study.
Canada looks like a great place to do delayed second dose studies later on when they start second dosing people. They have a shortage of vax so mainly stopped second dosing 2 months ago. Currently over 60% of the over 12 population have been vaccinated but of that total, 52% has only 1 vax and the other 8% are fully vaccinated.