One jab is not effective at all against most variants, really no point getting only one at all which is why you're only considered vaxxed after two. The booster is only recommended for waning antibodies 3 months after the first 2. Evidence so far point to the first booster being useful increasing antibody levels and the second booster not very effective. Now what is considered effective is a matter of perspective : prevention of death/hospitalisation/symptomatic infection/transmission. These 4 I've put in order of decreasing effectiveness. The 3rd jab is only useful if you're at least 3 months out past your 2nd. Whether you get jabbed that's a decision that should take into account : age, medical history, medications, whether it's important that you go out to restaurants a lot, whether you're a frequent international traveller. If you're under 40 and have no medical problems then its not so clear and that's why a discussion with someone who knows your history and situation is advised. Now if we're talking about someone with a haematological neoplasia like lymphoma or myeloma, for sure I would be recommending boosters. There's a lot of unknown about the virus that I find concerning : CT chest and MRI brain changes which persist after the infection. Could these lead to decreased lung function and chronic lung disease down the track, dementia? It remains to be seen what sort of burden on the health system long covid will have as well. We're flying blind in many areas against a virus which has thrown many surprises along the way.
