Find the Week Your Flu Shot Beats the Berlin Wave
Step to the week you could actually get a flu shot and see how much of Berlin’s last four flu waves would have reached you after you were protected. The board splits each winter at the day your shot starts working and names the week each wave peaked.
Weekly lab-confirmed influenza cases reported in Berlin, Robert Koch Institute open data (CC BY 4.0), seasons 2022/23 to 2025/26, read on 21 September 2026. Protection is counted from two weeks after the shot, in line with the RKI. Dates are moved onto the 2026/27 calendar. Timing guidance, not medical advice.
The RKI recommends a flu shot between October and mid-December, and the shot needs 10 to 14 days before it protects you. What that window does not tell you is when Berlin’s own wave arrives, and the answer changes every winter. In 2022/23 the Berlin peak was the week of 12 December. In the three winters since it came on 5 February 2024, 27 January 2025 and 19 January 2026. This board plots the weekly lab-confirmed flu cases reported in Berlin for those four seasons, stacked one above the other, and lets you step one week at a time through the calendar. Each winter is split at the day your protection would start: amber before, green after, with the two weeks the shot needs hatched in yellow. The number on the right is the share of that winter’s Berlin cases that came after you were covered. Switch to people 60 and over to see the same thing for the age group the STIKO recommends the shot for.
What the board plots
Four Berlin winters, one row each, from 2022/23 at the top to 2025/26 at the bottom. Each row is the weekly count of lab-confirmed flu cases reported in Berlin, scaled to its own peak so the shape and timing are comparable even though the winters were different sizes. The dark dot marks the peak week. The axis runs from mid-September to mid-April on this winter’s calendar.
Why the line sits two weeks after the shot
A flu shot takes about 10 to 14 days to build protection, so the dashed line is the week you get it and the solid line two weeks later is the week it starts to count. Everything to the left of the solid line is drawn amber, because those cases happened before you were covered. The hatched yellow strip between the two lines is the gap people forget when they book in the middle of a wave.
How to read the percentage
The figure on each row is that winter’s Berlin cases after your protection started, divided by all of that winter’s cases from reporting week 35 to week 20. A shot in the week of 2 November scores 95% or more in all four winters. The early 2022/23 winter is the one that punishes waiting: two weeks later it drops to 86%.
What it cannot tell you
Lab-confirmed cases are only the people who were tested and reported, so the real wave is larger. The board says nothing about how well the vaccine matches a given season, which varies, or about your own risk. It shows timing, which is the part you control. Whether you should get the shot, and which vaccine, is a question for your GP or pharmacist.