Wikipedia:Reference desk/Archives/Science/2021 July 25

= July 25 =

Covid booster
If you're already vaccinated, is the idea of a booster that you get an additional shot of the same vaccine that you had before? Or are they tweaking the vaccines to handle the current virus variants? I'm trying to find out if I should (or can) bring my mom in for a 3rd shot. She had 2 shots of Moderna in January (due to her age), so she is outside the 6 month window that I've heard. Thanks. 2601:648:8202:350:0:0:0:2B99 (talk) 05:02, 25 July 2021 (UTC)
 * You shouldn't ask us, you should ask your doctor. ←Baseball Bugs What's up, Doc? carrots→ 05:41, 25 July 2021 (UTC)
 * Certainly ask your dcotor (or her doctor, rather) for advice about her. But I've been reading a lot of news about COVID vaccines and I haven't heard of any of them being tweaked to handle current variants.  Rather, this is something that gets talked about as a possible future development.  Also, in some places nobody is being allowed a third shot yet, to conserve the supply for first and second shots.  So the doctor's advice may also depend on the rules where you are. --184.147.181.169 (talk) 05:50, 25 July 2021 (UTC)
 * I think there is not a vaccine shortage these days. There is consternation about having to throw out unused vaccines reaching expiration.  Main question was whether the vaccine boosters would be something new, which is a proper science question afaict.  I have to call my mom's doctor anyway though, so I'll ask him about getting her another shot.  He wasn't involved in getting her the initial shots though: that was done through the state web site, a big pain at the time.  By the time I was eligible I was able to get a walk-in dose with no appointment and not much waiting.  (I'm still in the 6 month period so not worrying about booster for now).  2601:648:8202:350:0:0:0:2B99 (talk) 08:06, 25 July 2021 (UTC)
 * As far as I can see (with all disclaimers regarding medical questions) this statement from the CDC and the FDA (8 July) is still valid. As I understand it, third shots are not even approved yet. --Wrongfilter (talk) 08:22, 25 July 2021 (UTC)
 * Vaccine supplies are still limited in large parts of the world. Even for the mRNA vaccines there are still many places which could handle them who are in big part limited by supplies. It's true there are a small number of countries like the US and Israel who have too much stock because they ordered and accepted a lot early on, but a significant chunk of their population is unwilling to get vaccinated, so they are now finding their vaccines are expiring. However if these countries start to compete for significant stocks again along with those who are getting close to them, this time for boosters, they will likely be mostly competing against countries where a significant chuck of their population even those particularly vulnerable ar3 unvaccinated. I don't think they will care even though it seems in the long term selfishness will harm them more, the only question is what level of evidence they will require before deciding to give booster shots. The US to their credit seem much more demanding of evidence than the UK. Yes I'm significantly more pessimistic than I was about 9 months ago that countries are going to screw us all with their selfishness. Nil Einne (talk) 13:27, 25 July 2021 (UTC)
 * Many countries even still have no access whatsoever to vaccine. It is conceivable that a deadly variant will emerge against which the current vaccines offer far too little protection before the world has reached global herd immunity so that the disease stops being a pandemic. --Lambiam 08:25, 26 July 2021 (UTC)


 * Right now, the French health authorities recommend a third dose for "severely immunosuppressed persons". (Link, in French.) I would hope they have some evidence to require that. Notice that "severely immunosuppressed" is not something random strangers can determine about your mother; this is different from "old".
 * We have an article about SARS-CoV-2 Delta variant. As explained at SARS-CoV-2_Delta_variant, it does have some mutations on the spike protein that make it more transmissible. It cites this research article, which, in my limited understanding, would support a claim that the antibodies created by current vaccination practices are less efficient at targeting the mutated spike. It would therefore be plausible speculation that vaccine efficiency is lower for the Delta variant.
 * This is only speculation though. The way to know would be to run a proper trial: take in an unvaccinated, uncontaminated population of proper size, give half of them a placebo and half of them a vaccine, see the ratio of how many catch Delta in the vaccinated vs. placebo arms; compare with the trials for the other variants. Such a trial will probably never be done due to ethical concerns: placebo vs. treatment trials are justified when the treatment might be more harmful than helpful, but now the null hypothesis is "vaccination against Delta is just as efficient as against the previous variants", not "vaccination does nothing against Delta". A two doses vs. three doses trials could probably be run, though.
 * I am not aware of any study of the secondary effects of a third dose, which would absolutely be needed before recommending such a schedule to the general population. I am however confident that an uncontrolled trial of third- (and fourth-, fifth-...) -dose-taking will soon be run in France, so that really bad side effects will probably be uncovered by journalists. You need to be vaccinated or pay for a nose swab every two days to go to cinemas and other pleasant places (maybe the nose swabs are still free until next month but regardless it's a pain), and there is a sizeable antivax population with more money than sense; so, it is probably only a matter of time before entreprising individuals realize that you can take the vaccine under someone else's name and carte vitale (ID for the French health system) for payment. Requesting an actual ID which some places do is hardly sufficient to foil this attack: ID cards are valid for fifteen years (carte vitale, forever) so the photo is likely out of date, the person whose face you are supposed to check is masked, and (at my place) ID verification was done by a town hall clerk (who is not trained for police purposes - they only want to check your name off the booking list). Tigraan Click here for my talk page ("private" contact) 12:29, 26 July 2021 (UTC)
 * Yes, there is evidence that immunosuppressed patients (a) are less likely to receive strong protection from COVID-19 even after a two-dose course of vaccinations; and (b) are likely to benefit from an additional booster dose.
 * Here's a paper from May 2021 that looked at 'breakthrough' cases of COVID-19 in solid-organ transplant recipients who had received complete (two-dose) immunization series: Ali et al.. Further, Boyarsky et al. (2021) reported that only about 54% of organ transplant recipients developed a detectible antibody response after two doses of mRNA vaccine.
 * Subsequent studies have looked at that subset of transplant recipients who had a weak or negligible response to two doses, to see if a second booster (third dose) would improve their antibody response. It turns out that, yes, about half of those weak or non-responders do develop significant antibody titers after a third dose. Benotmane et al., Werbel et al.. TenOfAllTrades(talk) 17:41, 27 July 2021 (UTC)

Potassium-argon dating of amber
Can it be done? There is certainly some potassium in amber, the main question would be whether the argon is trapped in the amber over geological times, so that the 40K/40Ar ratio can be used for dating, or if it diffuses through amber too quickly. And also, how much initial atmospheric argon is dissolved in the tree resin which becomes amber. Icek~enwiki (talk) 12:11, 25 July 2021 (UTC)


 * This one is behind a paywall and with a 1969 publication date, is quite dated, but the relevant text reads "Radioactive isotope age determinations of amber are not feasible since most of the samples are too old for C** [sic] dating, and the presence of adequate amounts of potassium to utilize the potassium-argon method has not been demonstrated as yet" and also "infrared spectrophotometry has so far been most extensively used in analyzing amber". Other sources I found seem to suggest that some degree of carbon dating does get employed with amber samples these days, but despite casting my net wide and looking through a number of paleobotanical and paleontological reference works, I could not determine if potassium-argon dating is feasible with today's methodologies. Snow let's rap 14:15, 25 July 2021 (UTC)