Visualization of Covid vaccine effectiveness. Except for the part about effectiveness going negative. Image courtesy of Adobe Stock.

A study of all Covid infections in Denmark over a three-week period of time shows vaccine effectiveness against Omicron not only evaporates but goes negative after three months. Yes, negative.

Unsafe Space on Substack – 1/19/22 – Do The Covid Shots Work Against Omicron? – The short answer, according to a study of all cases in Denmark occurring during three weeks last fall?

Covid shots only work against Omicron for around 30 days, falling off to minimal effectiveness at 90 days. After that you’d be better off not having a shot.

According to that research, sitting here in late January 2022, if you got your double shots earlier than October 2021 you are wide open to catching omicron. That might explain why almost everybody you know has been sick in the last month, regardless of their vaccination status.

More details…


The research report, which can be found here, looked at all PCR-confirmed Covid infections in Denmark between 11/20/21 and 12/12/21.

The researchers calculated vaccine effectiveness (VE) for the Pfizer and Moderna vaccines, with the calculation broken out into 30 day increments since full effectiveness. Fourteen days after the second shot is when one gains full effectiveness.

Researchers further calculated VE against the Delta and Omicron variants.


Their results show VE against Delta drops significantly from mid-80% down to mid 50s or mid 60s a mere four months after full vaccination.

VE against Omicron is radically lower. It starts off in the one-month range at a lower than the effectiveness against the Delta after four months. Pfizer starts at 55%, and Moderna is barely effective with a 37% VE up to one month.

Again, starting effectiveness against Omicron is lower than effectiveness against Delta in the four month range. Ouch.

While that is grim enough, look at the VE in the 61 to 90 day increments: barely worthwhile 10% VE for Pfizer and essentially nonexistent effectiveness of 4% for Moderna.

You ain’t seen nothing yet…

VE going negative

In the 91 through 120 day increments, in other words the fourth month after achieving full vaccination, the goal is harshly negative, with Pfizer’s going a horrendous negative 76% and Moderna scoring a somewhat less appalling negative 39%.

In other words, in terms of catching Omicron which is the most common variant circulating today, after the three month point you would be far better off not having a vaccination than with. According to the Danish study, you have a statistically significant higher chance of catching Omicron if you have been vaccinated than if you did not get the shots.

After 90 days, you’re more likely to get Omicron if you got vaccinated.

Effectiveness is terrible even before it goes negative.  The VE of both vaccines collapses at the sixty-day point (16% and 30%) and is essentially useless at 90 days (10% and 4%).

Oh yeah, as you take a look at the rapidly fading effectiveness even against the Delta variant, remember we were promised, yes promised, 95% effectiveness. Please note that not only does 95% not appear anywhere in the data, there is no data point even at the 90% level.

As for the booster, it basically gets you back to the one-month point of VE from the first round of shots. It would be a perfectly reasonable to assume the third shot will lose effectiveness just as fast.

I also infer this is the reason public health officials are positioning us for a fourth, and perhaps fifth shot, ad infinitum.

Data from Denmark basically is saying the shot is good against Omicron for 30 days and almost worthless out to 90 days, at which point you are worse off than without a shot.

Data points

Let’s look at the data which I extracted from the study. I will round to the nearest percentage point. I will not include the range of VE the researchers calculated at the 95% confidence interval. If you understand what is meant by 95% CI, please look at the research for yourself.

Last line on the table is the results for people who have a booster shot within the last 30 days.

Vaccine effectiveness for Pfizer, as calculated in the Danish study:

DaysVE OmicronVE Delta
1 – 30              55              87
31 – 60              16              81
61 – 90              10              73
91 – 150           (76)              54
booster 30              55              81

Vaccine effectiveness for  Moderna, as calculated in the Danish study:

DaysVE OmicronVE Delta
1 – 30              37              88
31 – 60              30              82
61 – 90                4              72
91 – 150           (39)              65
booster 30              83


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