This is a difficult decision. As @CMO_England says, delaying 2nd dose should save more lives though given:
1. Virus is out of control
2. Bottlenecks mean more people won’t be vaccinated sooner
3. First dose provides good protection

If we had avoided 1 & 2 then no need to delay https://twitter.com/sandyddouglas/status/1344949258483621888

Effects on transmission of different dosing schedules remain unknown but it stands to reason that if vaccination reduces transmission vaccinating more people with one dose more quickly should have more of an impact in terms of controlling the epidemic too (also preventing deaths)

another good thread here on delaying second vaccine dose worth reading https://twitter.com/VirusesImmunity/status/1345086669607890945?s=20