This is entirely unsurprising. The action of vaccines is to pre-prime the body to fight the virus, like letting students read the answers to the test the week

This is entirely unsurprising. The action of vaccines is to pre-prime the body to fight the virus, like letting students read the answers to the test the week before. The result is not some kind of impermeable Star Wars shield, but a reduced likelihood that any one exposure will result in an infection. So, given a 90% effectiveness rate, it means that an exposure level (e.g., getting directly in the way of the coughs of a contagious person) that would typically infect 10 of 10 people, will now only result in only one infection of vaccinated people. However, if those vaccinated people expose themselves 10 times to the same viral load, they are now highly likely to get infected. Since living in the same household as an infected person literally creates multiple large exposures per day for the contagious period, it is no surprise that many vaccinated people will get infected in that situation. This does NOT mean the vaccine is ineffective, it is simply a limitation of the biology to be aware of. Reducing the household infections — continuous exposure — from 38% down to 25% is a very strong effect, cutting the infection rate by 1/3, or leaving unvaccinated people 50% more vulnerable. Moreover, these effects are multiplied. The 50% greater rate of household infections for the unvaccinated means 50% more people going out in the world infecting more people. This can have a massive effect on the R0 value, extending the pandemic greatly over the vaccinated rates. So, yes, the lesson should definitely be to vaccinate everyone, and make sure that they keep up to date on their boosters.