Thread by @DrZoeHyde

Is the pandemic really over? What’s likely to happen over the next 12-18 months? The UK’s Scientific Advisory Group for Emergencies (SAGE) outline four possible scenarios ranging from optimistic to pessimistic.

Here’s what they describe…🧵
gov.uk/government/pub…

In the best case scenario, the vaccines retain their effectiveness against new variants (which do not show increased transmissibility or severity). Antiviral drugs stop people from getting really sick and these drugs remain effective. Only minor seasonal/regional outbreaks occur.

In the central optimistic scenario, waves of infection continue to occur, driven by waning immunity and/or new variants. There will be good & bad years; some variants will cause more severe disease. Immunity protects most people but resistance to antiviral drugs begins to appear.

In the central pessimistic scenario, there are repeated, disruptive waves of infection driven by the unpredictable emergence of variants. Existing immunity and new vaccines continue to protect most people, but resistance to antiviral drugs is widespread.

In the worst case scenario, high levels of human transmission, incomplete global vaccination, and transmission among animals leads to repeated emergence of variants (some of which cause more severe disease and escape immunity). There are increased long-term impacts of infection.

Regardless of which scenario ends up being correct, SAGE assume it will take considerable time before a stable state is reached (2 to 10 years).

They write that the transition phase is likely to be “highly dynamic and unpredictable.”

My 2 cents on the report: the best case scenario doesn’t seem realistic. It’s inconsistent with what’s occurred so far (at least with regard to transmissibility & antigenic evolution). I think elements of the central optimistic scenario are unlikely too, particularly seasonality.

Based on our experience with SARS-CoV-2 to date, the central pessimistic scenario seems most likely to me. However, I think one element of the worst case scenario - increased long-term impacts following infection - may also be correct.

This is why I think we need a #VaccinesPLUS strategy to keep cases low until we can develop more effective vaccines (particularly intranasal vaccines that may better prevent infection & transmission). We can do more with simple measures like ventilation that don’t burden people.

The key take-home message is the pandemic is far from over, unless we’re lucky enough that the best case scenario is correct. But trusting our luck is unlikely to be a winning strategy. If we want the pandemic to end, we need to do the work (#VaccinesPLUS) to make that happen.