Nasal boosters?
By 
This is promising:
On the outskirts of this centuries-old Indian city, a world away from its congested roads and cacophony, the gleaming modern laboratories of Bharat Biotech are churning out a Covid vaccine that would be sprayed into the nose rather than injected into the blood.
Currently available vaccines produce powerful, long-lasting immunity against severe illness, as several studies have recently shown. But their protection against infection from the coronavirus is transient, and can falter as new variants of the virus emerge — a failing that has prompted talk of regular booster shots.
Nasal vaccines may be the best way to prevent infections long term, because they provide protection exactly where it is needed to fend off the virus: the mucosal linings of the airways, where the coronavirus first lands.
Bharat Biotech is among the world’s leading vaccine manufacturers. Its best known product, Covaxin, is authorized to prevent Covid in India and many other countries. But its experimental nasal vaccine may prove to be the real game changer.
It doesn’t look, at this stage, that this would solve the needle reluctance problem — people will still need to take the classic vaccines. But the nasal vaccines could prove to be boosters that are effective at preventing infection as well as severe illness, and that would be a critical breakthrough in its own right.