president biden of late. watch. >> you can protect yourself, and you should protect yourself quite frankly. get vaccinated. get boosted. there are plenty of booster shots. >> laura: tonight, professor, from bloomberg, repeat booster shots spur european warning on immune system risk. repeat boosters every four months could eventually weaken the immune system and tire out people according to the european medicine agency. big survey and study on that. your reaction? are you surprised? >> no, i mean, there is no good clinical evidence that this idea that we're going to have to take shots one after another after another after another for months on end forever, there is no evidence at all to suggest that that's the right regimen. i do believe that the vaccines protect against severe disease and for people who are older they are still quite wise. even for older people it might be wise to get a single booster but i do not think it's a good