Pfizer says blood samples showed a third dose of its vaccine provides significant protection against
Source: New York Times
Pfizer and BioNTech said Wednesday that laboratory tests suggest that three doses of their coronavirus vaccine offers significant protection against the fast-spreading Omicron variant of the virus. The companies said that tests of blood from individuals who received only two doses found more than a 25-fold reduction in antibody levels against the Omicron variant compared to an earlier version of the virus.
That finding indicates that two doses alone “may not be sufficient to protect against infection” by the new variant, the companies said. But the blood samples obtained from people one month after they had received a booster shot showed neutralizing antibodies against the Omicron variant comparable to the levels of antibodies against a previous version of the virus after two doses, the companies said in a statement. At the same time, the tests suggested that the mutations in Omicron do not appear to significantly affect T cells — another critical part of the immune system’s response.
That suggests “vaccinated individuals may still be protected against severe forms of the disease” after only two doses, the companies said. The results seem to underscore the importance of booster shots in combating the new variant. “Our preliminary, first data set indicate that a third dose could still offer a sufficient level of protection from disease of any severity caused by the Omicron variant,” said Dr. Ugur Sahin, the chief executive officer of BioNTech, Pfizer’s German partner.
The results come one day after a preliminary report on laboratory experiments in South Africa found Omicron seemed to dull the power of the Pfizer’s vaccine. Those experiments also hinted that people who have received a booster shot might be better protected. The Omicron variant has now spread to dozens of countries, and while the Delta variant is still overwhelming dominant here, the Biden administration is bracing for Omicron’s impact.
Read more: https://www.nytimes.com/live/2021/12/08/world/omicron-variant-covid/pfizer-says-blood-samples-showed-a-third-dose-of-its-vaccine-provides-significant-protection-against-omicron
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we are still only a couple months out from when you could have gotten that booster so there should be time to evaluate how that goes (particularly for those who are still in the mix/match trials who had Janssen's (J&J) vaccine).
Those who got Pfizer or Moderna in a "2-dose series", generally started those much earlier, and only started getting a "3rd dose" 6 months (or later) after their 2nd dose once that was approved in August.
So at this point, the "importance of 3 shots" is only for the mRNA vaccines. From what I gathered, a mRNA "booster" to Janssen's vaccine provided a very robust response and you are probably good to go for the time being (unless you are very immuno-compromised and in that case, I think they are still trying to get data from what happens after an initial booster - whether using another Janssen or one of the mRNAs). 
Which for Pfizer would mean a "3-dose primary series" plus a "4th dose" (that they are calling a "booster" although it is the same concentration as the previous doses).
This is actually reflected on the top row of that chart.
The first column shows a "2-dose primary series" as the initial dosing (with a default timing between dose 1 and dose 2 of 21 days, although in your case, the 2nd dose was a week earlier), and then in the second column, they list what they are calling "an additional dose for the immuno-compromised" at least 28 days after the first 2, and finally in the third column they show what they are calling a "booster dose" at least 6 months after the initial doses.
... mostly. Still very confusing though.
Just tell me where I need to be and what I need to do and I'll be there to get my shot/s.
Yes - there appears to be that 6-month interval between the first 3 and a 4th one. At that point, we would be into a new year since the initial large group of vaccines were done, so we'll have to see at what point people are told to "start over" for a new year's worth of protection (I know they don't want to think about that 
).
Since I wanted to stay with Moderna for a booster and that wasn't approved for "regular" booster doses until the 3rd week of October, I waited until a couple weeks after that approval week so that I could also get the flu shot with it too.
The timing was pretty good since I reached the 6 months post-1st/2nd doses that same week Moderna was approved for the non-immuno-compromised booster, so I could plan for it at a closer location to where I live, making sure that where I got the vaccine also carried Moderna (some sites only carried Pfizer).
Stay safe!