4 ms·
This is all about antibody neutralization titers. Researchers mix diluted blood plasma with viral samples, and then see whether it can grow in cell cultures.
by mlyle 5y ago
This is all about antibody neutralization titers.
Researchers mix diluted blood plasma with viral samples, and then see whether it can grow in cell cultures. They figure out the concentration of plasma needed to neutralize all the virus.
2 doses of the vaccine produces plasma that can still neutralize the virus, but it requires 20x as much plasma on average. In turn, this means that the virus is more likely to be able to replicate and infect new cells before all the virus is neutralized.
However:
- There is still antibody efficacy against the virus, just not nearly as much.
- Memory B cells have a head-start at further developing specific immunity to new variants.
- This ignores the effect of T-cell mediated immunity.
- This mentions evidence that people who were previously infected and vaccinated have good neutralizing titers against Omicron.
- Other evidence suggests people who are boosted have much better neutralization titers against Omicron. That is, boosting doesn't just increase the number of antibodies, but increases the breadth of antibody protection.
- yonaguska 5y agoCan you explain how it increases the breadth of antibody protection if the booster is exactly the same as the original shot? Is there any way to know whether that increased breadth of antibody protection isn't coming from a post vaccination exposure that wasn't tested for not tested? Since vaccinated people aren't generally required to do asymptomatic testing, let alone symptomatic testing in many places.
- mlyle 5y ago> Can you explain how it increases the breadth of antibody protection if the booster is exactly the same as the original shot? It's complicated! The short answer I gave elsewhere: B cells aggressively replicate and mutate in response to pathogens, and those that match are selected for. Repeating this process gets more B cells, but also broader varieties of resultant antibodies matching not just the original pathogen but things that are close to it. > Is there any way to know whether that increased breadth of antibody protection isn't coming from a post vaccination exposure that wasn't tested for not tested? Yes. We collect plasma from people, and then test it against a variety of variants in assays. We have plenty of old plasma to do this with. Indeed, there's some evidence that many people who were both infected with SARS-CoV-1 and subsequently vaccinated against SARS-CoV-2 may have exceptionally broad immunity to coronaviruses, not isolated to just SARS-CoV variants but also to wild-type coronaviruses circulating in animals and human coronaviruses causing the common cold.
- yonaguska 5y agoThanks! This clears up a lot for me.
- flatiron 5y agoI want to compliment your responses. Factual and non aggressive which is needed in this time. Thank you.
- mlyle 5y agoHey, thank you so much! I try. I also have to confess that my understanding of this subject matter is far from perfect (and even experts' understanding is relatively limited).
- headsoup 5y agoI thought that was what these vaccines specifically don't do: they select for the spike protein of the original variant and ignore others, whereas natural infection generates a broader response that will target a variety of proteins. Has that changed?
- smnrchrds 5y agoIt's something I have seen a lot of people say here on HN, but I don't know if it's true. If having the whole virus was more effective than just the spike protein, wouldn't Sinopharm and Sinovac—which are inactivated virus vaccines—be more effective than Pfizer and Moderna? We still don't know their efficacy against Omicron, but they were less effective than mRNA vaccines against all previous variants.
- headsoup 5y agoInitially perhaps, but do we have good longer term data on how the sinovac holds up, given we're now saying Pfizer needs to be 3-monthly and Moderna is a much stronger dose? I think there was some over-selling of the mRNA vaccines that needs strong follow-up review given the state of the virus vs last year without vaccines with a more potent variant.
- dukeofdoom 5y agoHow can this possibly be true, when we now have real world data from Ontario. The case count of the vaccinated has now surpassed the unvaccinated and seems to be growing exponentially. 3rd graph. 32.39 cases / 100,000 people double vaccinated vs 31.93 / 100k of the unvaccinated. https://covid-19.ontario.ca/data?fbclid=IwAR2pRUq9GN9EEoDTm0OetspYalQy0Otcc41JS6b-L9BnzLOdhl1eZ1L4FHg https://covid-19.ontario.ca/data?fbclid=IwAR2pRUq9GN9EEoDTm0... The vaccines don't seem to confer any lasting difference.
- mlyle 5y agoThat's interesting data. It's not in agreement with other jurisdictions, so far. Elsewhere, including South Africa, we see (poor quality) protection from vaccination. One concern with observational studies: people who choose vaccination don't behave exactly the same as people who don't. They may assume more risks out of perceived safety. They may also be more likely to test or seek medical care. This is why, at a minimum, you need case control to start to believe the conclusions.
- dukeofdoom 5y agoUnlikely, in Ontario the unvaccinated as a group have to test 2 or 3 times a week keep their jobs. If anyone is more likely to report a case it's the vaccinated.
- mlyle 5y agoOK. We'll see. I think there's lots of confounds-- e.g. vastly differing vaccination rates among children vs. the population at large. In any case, we have actual case control studies showing mRNA vaccine efficacy against illness and particularly against severe illness from Omicron. They disagree on the amounts, and in some cases the numbers are not thrilling (30%), but there's no studies so far implying no efficacy. The study we're discussing here concludes its abstract with: "These data support the notion that, provided high neutralization capacity is elicited by vaccination/boosting approaches, reasonable effectiveness against Omicron may be maintained."