The idea that the Covid 19 virus could be eliminated is as daft as the notion that Covid vaccines are useless/harmful/a plot to control the world. Yet the seemingly respectable and knowledgeable  people who espouse the former idea appear regularly on TV and in the media, whereas those that believe the latter are shunned.

The second group frequently argue that the fact that there are some diseases, such as the common cold and HIVAIDS, for which there is no vaccine (yet) means that no effective vaccines for Covid could have been developed so quickly and that therefore the whole thing is a con. The Zero Covid lot think it is possible to eliminate a pathogenic virus completely, as has been done with smallpox, so why not Covid?

Smallpox elimination required unprecedented global co-operation mediated by the WHO, but even if this could be assured for Covid, there are technical reasons why it was possible in the first case, but impossible in the second.

The reasons smallpox was eliminated successfully are:

1.    Smallpox cases were readily identifiable clinically just by looking at the characteristic skin lesions. Therefore it was easy to tell who had it, even without laboratory testing. There was no asymptomatic transmission.

2.    There was a good, safe, stable and easily transportable vaccine in the form of the Vaccinia virus, known since the eighteenth century. Moreover, it produced life-long immunity.

3.    There was no animal reservoir for smallpox, so once it was eliminated in humans it was gone for good

4.    For all these reasons, it was possible to ring-vaccinate contacts of cases (because they were so readily identified). This strategy was critical in mopping up the last cases, as mass vaccination was only partially successful in certain countries. Ring-vaccination involved identifying a case, isolating the individual, and then vaccinating all contacts and contacts of contacts, so that the virus had nowhere to go.

The elimination of smallpox by 1980 was an unprecedented public health triumph.

Assuming the same level of global co-operation led by the WHO (a big assumption) could Covid be eliminated in the same way? Unfortunately probably not for the following reasons:

1.    Covid cases can only be identified by testing. As there are asymptomatic cases which can probably still transmit the virus, any ring-vaccination strategy would mean testing everybody, a waste of scarce resources. Mass vaccination, with its limitations, is the only alternative.

2.    At least some of the available vaccines are stable at fridge temperatures (except for Pfizer) and could in theory be used world-wide, but the length of protection is currently unknown, as is their efficacy against variants.

3.    Although the jury is still out about Covid’s origins, it is very likely that there are animal reservoirs.

The Zero Covid strategy might work in the short term in countries such as Australia and New Zealand as long as isolation could be enforced, but the nature of the virus and its disease makes world-wide elimination impractical. A strategy of mass vaccination should eventually enable us to live with it as we do with influenza.

Remains the question: why are the Zero Covid advocates pushing this idea?

 

 


 

Dr Jacinta Skelly has worked as a virologist in Ireland and abroad for 35 years