# Any reason to pick Pfizer over Moderna, or does it not really matter **URL:** \ **Category:** The Quarantine Zone\ **Tags:** covid-quarantine\ **Created:** [March 21, 2021, 5:38pm UTC](https://boards.straightdope.com/t/any-reason-to-pick-pfizer-over-moderna-or-does-it-not-really-matter/938354 "2021-03-21T17:38:00Z")\ **Posts on this page:** 3\ **Page:** 3
**Author:** ![Tamerlane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tamerlane/32/7602_2.png) [@Tamerlane](https://boards.straightdope.com/u/Tamerlane)\ **Post date:** [March 24, 2021, 3:51am UTC](https://boards.straightdope.com/t/any-reason-to-pick-pfizer-over-moderna-or-does-it-not-really-matter/938354/41 "2021-03-24T03:51:11Z")
> [@hajario](#): > > My second choice is Pfizer since it’s three weeks between the two shots and supposedly the side effects are generally not as bad after the second shot. > [@nelliebly](#): > > I got Moderna. I initially would have preferred Pfizer due to the one-week-shorter interval, but frick, I got Pfizer and they scheduled me a month apart regardless 😉. I suspect because the county network I used uses both, they schedule both appointments at the same time when you sign-up and they don’t bother to figure out ahead of time which vaccine you’ll end up with for your first shot. I got mine at a quite efficient county health center and in the little group I was in all 1rst shots were getting Pfizer, but a couple of 2nd shot people were getting Moderna. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 24, 2021, 11:29am UTC](https://boards.straightdope.com/t/any-reason-to-pick-pfizer-over-moderna-or-does-it-not-really-matter/938354/42 "2021-03-24T11:29:29Z")
> [@puzzlegal](#): > > One shot of either RNA vaccine gives you decent immunity, at least for a short time. I guess I’ll wait until two weeks after the second shot to do anything exciting, but I’ll be a lot less anxious three weeks after the first one, for any of the ones currently authorized in the US. My thoughts exactly. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [March 27, 2021, 2:14am UTC](https://boards.straightdope.com/t/any-reason-to-pick-pfizer-over-moderna-or-does-it-not-really-matter/938354/44 "2021-03-27T02:14:10Z")
> [@puzzlegal](#): > > > [@Wesley\_Clark](#): > > > > The fact that Pfizer only requires three weeks between shots vs 4 weeks for Moderna for example is a reason to pick Pfizer if possible. > > I’m pretty sure that’s an artifact of the testing regimen they each chose, and not due to an intrinsic difference in how they work. Of course, until we have additional evidence, it’s prudent to use the protocol used in the testing. But we’re going to have a lot more evidence in a few months (from the UK, and perhaps Canada, where they are stretching out that timing) and I’ll be shocked if they don’t work at least as well with a longer lag between the initial and second jab. Possibly. Its actually a 2 week shorter period for full immunity from Pfizer. The Pfizer vaccine has a 21 day period between doses vs 28 for Moderna, but also according to studies you are at ~95% immunity one week after the second dose, vs 2 weeks after the second dose for Moderna. > **[How long does it take to have immunity after the second vaccine dose? - How Long...](https://www.healthline.com/health/how-long-after-the-second-dose-of-the-covid-vaccine-are-you-immune#timeframe)** > > There are many different COVID-19 vaccines in development worldwide. In the United States, the Food and Drug Administration (FDA) has so far authorized three COVID-19 vaccines for emergency use. | If you get the Pfizer-BioNTech or Moderna vaccine,... > The Pfizer-BioNTech clinical trial evaluated vaccine effectiveness 1 week after participants had gotten their second dose. Researchers found that the vaccine was [95 percent effective](https://www.nejm.org/doi/full/10.1056/NEJMoa2034577) at preventing COVID-19 at this point. > > The Moderna clinical trial looked at vaccine effectiveness 2 weeks after participants had received their second dose. At this point, the vaccine was found to be [94.1 percent effective](https://www.nejm.org/doi/full/10.1056/NEJMoa2035389) at preventing COVID-19. However I don’t know how they picked those dates or if its more effective earlier. Either way I already got my first vaccine and am looking forward to the second. [Previous page](https://boards.straightdope.com/t/any-reason-to-pick-pfizer-over-moderna-or-does-it-not-really-matter/938354.md?page=2)