[EvaH (OP)]

Tom asks:

I was reading today about how the Johnson and Johnson and the Oxford vaccine both use viruses as vectors to transport the code for the RNA spike protein. Both of these have been modified to be non-replicating. This got me thinking, couldn't the vector viruses be modified to be replicating and theoretically spread the RNA spike protein amongst the population creating immunity? Surely quicker, easier and cheaper than vaccinating millions of people individually. I imagine this has already been throught of and wondered what the limitations of it might be?

What do you think?

[charles1948]

I'm not sure what you mean by "virus vectors".  Do you envisage a kind of "anti-virus" virus.

A "friendly" virus, which would detect, attack and destroy "hostile" viruses such Covid-19

In a similar way to military "anti-missile" missiles, which shoot down hostile missiles

Is that biochemically possible?

[Bored chemist]

Well... imagine you managed to spread an epidemic of cowpox.
You would vaccinate everyone (or nearly everyone) against smallpox, but the problem would be the damage done by the "vaccine".
It might be possible but it would be utterly unethical.

The first person who was in any way harmed by an infection that you unleashed, and which they didn't consent to, could have you jailed for common assault (and  a class action would sue you into bankruptcy as well).
And, since essentially any infection is going to, at least, give you a headache, the idea is untenable.

[evan_au]

couldn't the vector viruses be modified to be replicating and theoretically spread the RNA spike protein amongst the population creating immunity? Surely quicker,

The "preventative" virus would need to spread more quickly than the SARS-COV2 virus - only SARS-COV2 has a head start of around 100 million (as of this week).
- That means the new virus would need to cause a more severe cough and sneezing, to spread further and faster
- It would be very hard for the preventer virus to spread now that most people have caught on to the idea that masks and social distancing reduce the spread of SARS-COV2. And anyone with viral symptoms must stay home.

There have been cases where live virus has been used in a vaccine: an attenuated polio virus was used for vaccination.
- However, the attenuated virus still sometimes caused paralysis
- And the attenuated virus started spreading beyond the people being vaccinated
- So today, they not only have to hunt down the last cases of "wild-type" polio, they have to detect and prevent the spread of the attenuated vaccine virus, too
- Even the attenuated virus is a risk to immune-compromised patients, eg transplant recipients, AIDS victims and cancer patients

I think a non-replicating vaccine is the preferred solution.

[set fair]

I think it's a decent idea, there would be casualties but a lower death rate (apeals to one's fascist tendancies). Hard lockdown for a month, then vacinate a milion people from ten days in. When the vaccinated test to be infectious for the vector virus, they vist other households with a sprig of mistletoe.

An alternative would be a live Sars CoV2 virus with some of the nasties removed.

What I do think is that this ought to be thourghly looked into before the next pandemic.

[set fair]

'Ere Tom, you reckon that's what they did in the US, on the quiet, to bring the cases dowm?

[evan_au]

What I do think is that this ought to be thourghly looked into before the next pandemic.

hmm...  and what sort of virus do you think the next pandemic will be?
- Some sort of influenza, from birds or pigs or???
- Another coronavirus, this time caught from bats via dogs or donkeys or???
- Some other virus entirely???

There is no point in infecting everyone with dog coronavirus if the next pandemic is (say) donkey coronavirus.
- There is a lot of point in vaccinating everyone against the common strains of influenza that are starting to spread worldwide
- And if COVID-19 variants continue to multiply, it will be very sensible to vaccinate everyone against the common strains of COVID-19 that are starting to spread worldwide.
- The UK variant of COVID-19 seems to be eliminating other COVID-19 variants in the countries where it is introduced, so maybe we allow the UK variant to eliminate all the other variants, and then we vaccinate against the UK variant?

[CliffordK]

There are a few vaccines that use full live attenuated viruses which can actually spread.

Cowpox/Horsepox, & the Oral Polio vaccine were mentioned above (Injected Polio vaccine isn't a live virus).

Keep in mind that a lot has changed with vaccination in the last century or two.  So we don't need to simply choose a related animal virus, or try to force attenuation of a virus via passing it through animals for several generations before reintroducing back to people.

Keep in mind that the current COVID pandemic was a bat virus that jumped to humans, and has now evolved to become more infectious to humans.

There would be extraordinary liability if a lab created the next pandemic through a vaccine in their name.

I am a bit surprised that we are still using the attenuated polio vaccine, although it is very effective with a single dose rather than multiple doses with IPV.  While reasonably safe, we do have several vaccine derived paralytic polio outbreaks.