What are your thoughts on the delayed second dose of the COVID-19 vaccine?

[bread]

Some provinces are now delaying the second dose of the COVID-19 vaccine by up to 16 weeks, as per the federal recommendation that it was okay to do so based on their data.  I've been reading some interesting discussion about this, and wondering what everyone's thoughts are.

I agree it makes sense to vaccinate as many people as we can as quickly as possible.  However, this seems like an experiment given no other country (or trial) has delayed the second dose by this long - what will this mean for length of immunity and both short- and long-term efficacy?  I know they've quoted data suggesting that one dose has high efficacy at 2 months post-vaccine, but this data doesn't seem to be easily accessible to the public, and even if it was, can we be confident that 4 months is okay, too?  There's also the interesting question regarding consent, and whether people who received their first dose with the understanding that they would have their second dose within 3-5 weeks would have preferred to wait until more data was available had they known their second dose would not be for 16 weeks.  

I think this is an interesting discussion, and would like to hear others' thoughts on this here, too!

[Gimli]

I know that AstraZeneca doesn't have good reputation today after their press release where they said that their interim analysis showed a 79% efficacy for symptomatic COVID while it was dated information. https://www.astrazeneca.com/content/astraz/media-centre/press-releases/2021/astrazeneca-us-vaccine-trial-met-primary-endpoint.html Anyway, in their first trial in the UK, SA and US they seem to have found that delaying the seconde dose had en effect of increasing efficacy "Evidence shows protection starts from approximately 3 weeks after first dose of vaccine and persists up to 12 weeks. A second dose should be given at a 4-to-12-week interval after the first dose, with evidence that efficacy increases with longer dosing intervals." You can read in the document they submitted to Health Canada here.  https://covid-vaccine.canada.ca/info/pdf/astrazeneca-covid-19-vaccine-pm-en.pdf  From an immune standpoint I don't think delaying the second dose will be a bad thing. 

As for your question, this paper shows pretty good efficacy at reducing hospitalisation after a single dose up to 42 day after the shot. https://www.ed.ac.uk/files/atoms/files/scotland_firstvaccinedata_preprint.pdf I know it's not 4 months, but if someone has a paper showing antibody titers after a single dose over a 4 month period i'd like to read it. 

Finally, I though that paper was quite interesting considering the approach that we have of delayed second dose for everyone https://www.medrxiv.org/content/10.1101/2021.02.26.21252512v1.full.pdf+html . Around 35% IgG positivity for neutralizing Ab in the 80 yo population at 21 days + with Pfizer/BioNTech, but that number goes to 88% in the same age group after the second dose. Maybe we're not protecting older people like we think we are. 

[bread]

On 3/23/2021 at 10:42 PM, Gimli said:

I know that AstraZeneca doesn't have good reputation today after their press release where they said that their interim analysis showed a 79% efficacy for symptomatic COVID while it was dated information. https://www.astrazeneca.com/content/astraz/media-centre/press-releases/2021/astrazeneca-us-vaccine-trial-met-primary-endpoint.html Anyway, in their first trial in the UK, SA and US they seem to have found that delaying the seconde dose had en effect of increasing efficacy "Evidence shows protection starts from approximately 3 weeks after first dose of vaccine and persists up to 12 weeks. A second dose should be given at a 4-to-12-week interval after the first dose, with evidence that efficacy increases with longer dosing intervals." You can read in the document they submitted to Health Canada here.  https://covid-vaccine.canada.ca/info/pdf/astrazeneca-covid-19-vaccine-pm-en.pdf  From an immune standpoint I don't think delaying the second dose will be a bad thing. 

As for your question, this paper shows pretty good efficacy at reducing hospitalisation after a single dose up to 42 day after the shot. https://www.ed.ac.uk/files/atoms/files/scotland_firstvaccinedata_preprint.pdf I know it's not 4 months, but if someone has a paper showing antibody titers after a single dose over a 4 month period i'd like to read it. 

Finally, I though that paper was quite interesting considering the approach that we have of delayed second dose for everyone https://www.medrxiv.org/content/10.1101/2021.02.26.21252512v1.full.pdf+html . Around 35% IgG positivity for neutralizing Ab in the 80 yo population at 21 days + with Pfizer/BioNTech, but that number goes to 88% in the same age group after the second dose. Maybe we're not protecting older people like we think we are. 

Thank you so much for posting/sharing all this!! I hope we are on the right track in doing this, and that we don’t see any negative effects from waiting so long for the second dose. I came across this today, too, which furthers your last point about the single dose being much less effective for our older population, which I think is concerning: https://financialpost.com/diane-francis/diane-francis-health-canada-must-stop-endangering-lives-by-delaying-second-doses-of-covid-vaccines