Expert in infectious diseases answers your vaccine questions amid hopes jab can end Covid-19 nightmare

News that a huge breakthrough has been made in the hunt for a Covid vaccine was welcomed all over the world.

Early trials of a vaccine from US drugs giant Pfizer and German tech firm BioNTech showed it was 90% effective against the coronavirus.

If these initial findings bear fruit it would mean Britain could take its first steps on a return to normality soon with some experts daying the country has an 80% chance of that happening by Easter.

The UK government has secured access to 40 million doses with 10 million – enough for five million Brits as everyone needs two doses – set to become available in the UK by the end of the year, with the NHS and Army on standby to help roll it out.

Dr Mike Tildesley , associate professor in infectious disease modelling at the University of Warwick, spoke to readers of the Mirror to address common questions about the vaccine.

What do we know about the vaccine?

What we’ve seen is this suggestion that there’s a 90% effectiveness, but it’s a little bit unclear what that means.

It’s very important to remember that the data that’s now out has only come from a relatively small batch that’s come seven days after the second vaccination.

That’s cautiously good news but we need to wait for subsequent weeks worth of data to come in to see if that figure is believable.

Is it dangerous?

We need to be very careful about this, just because a vaccine passes phase three clinical trials, which of course this hasn’t done yet, that doesn’t mean it is safe to use.

What happens after this is regulatory approval which means it gets endorsed as a safe to use vaccine.

It’s important to remember with vaccines that sometimes when we get vaccinated, you’re being essentially vaccinated with what’s very similar to a low dose of the virus, so some people may start to develop some mild symptoms that are similar to Covid.

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That doesn’t mean it’s dangerous.

Of course we would assume that a vaccine would not be endorsed for use on a large scale unless we were absolutely sure that it didn’t pose any risk to the population.



Dr Mike Tildesley said it's not clear yet how long the vaccine will provide protection for
Dr Mike Tildesley said it’s not clear yet how long the vaccine will provide protection for

Will it be like the flu vaccine?

The flu vaccine that a lot of us get vaccinated with every winter, every winter we get a different strain of flu that comes along, and you have to have a new vaccine for that.

It may be that if we see coronavirus mutating every year, it might be that every year we’ll need a new vaccine.

What I would say it that once we have a vaccine developed in the first place it will be significantly easier for future vaccines to be developed for any future coronavirus outbreaks in subsequent years.

Doesn’t your immune system work like this anyway without the vaccine?

In a sense yes, it does. We only have to go back to March and there was the whole debate around herd immunity

Herd immunity is what we’re striving to achieve, through any vaccination campaign, that’s what you’re trying to get to.

It happens through people getting infected and developing immunity because they’ve recovered, or being vaccinated and developing immunity.

What we don’t know is how the immune system responds to being infected and developing antibodies or being vaccinated and developing antibodies.

In both cases it’s unlikely that antibodies will be lifelong, but it’s unclear if they will wane faster through infection or through vaccination.

Who will be able to get the vaccine first?

This is one of the big unknowns that hasn’t come out of the study.

We’re not sure whether it works more effectively in elderly people.

If it does, the optimal strategy should be to reduce the risk of hospitals being overwhelmed and limiting the risk of people dying from the disease.

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The best way to do that, particularly if we have a limit on the number of doses, is to target the really elderly and the people with underlying health conditions.

Then possibly frontline workers such as healthcare workers, people who are more exposed.

It’s likely that younger people like those under 50 will be towards the bottom of the priority list.

If we started to vaccinate the most vulnerable we will very very quickly see the largest impact of the pandemic in terms of hospitals being overwhelmed and people dying will be greatly reduced.

What level of takeup is needed to achieve herd immunity?

This all comes back to the R number.

The R number is crucial, let me give a really simple example. If the R number is two, this means every time someone is infected you infect two people, if you were to vaccinate half the population you’d get the R number below one.

Let’s say to make the maths easy it’s 100% effective and you vaccinate just over half the people, the R number goes below 1 and the disease dies out.

Now for coronavirus the early reports were suggesting that the R was between 3 and 4, so what that means is that 70% immunity is needed in order for us to get to that magic herd immunity.

If the vaccine is 90% effective, you need slightly more than 70% to take on that vaccine.

If 20% of people refuse the vaccine, what is that going to mean?

As an individual you’re most likely to be protected, but on a population level the likelihood is that you’ll still see outbreaks.

If we’re seeing 20% of people unlikely to take it, it’s very worrying, as it pushes you very very close to that 70%.

If you don’t know the effects of the vaccine and there is that much unknown then why would you give it to the vulnerable?

I think that’s an extremely good point and it’s why we can’t say we’re going to roll out the vaccine.

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There’s a lot of unknowns still, we need to be absolutely sure there’s no side effects.

It seems that based on the information we have that’s not the case. We have a pretty good indication it’s relatively safe, but we need to know it’s effective for the elderly and vulnerable.

This has been done a lot more rapidly (than normal) but this crucial regulatory stage needs to happen beyond these phase three clinical trials.

My hope and my belief would be that a vaccine wouldn’t be endorsed for use until we know it’s safe and effective.

Will the vaccine mean that Covid is gone forever?

Not necessarily. It really depends what happens, there is a suggestion we could get the virus mutating with new strains in subsequent years.

We might have this virus circulating every season, and we’d need a new vaccine.

Most of us in our lifetimes will get infected with a number of coronaviruses like coughs and colds.

It’s mostly the case that viruses mutate into milder forms, but for longer term protection we might need regular vaccinations.

Are we better prepared for a future pandemic?

In a sense we are just as susceptible but I’d say we’re better prepared.

We’ve learned an awful lot, many of the changes we’ve made in terms of policy are unprecedented in our lifetimes, we’ve not experienced these kind of restrictions in peacetime.

From a science perspective, in terms of the collaborative nature that’s grown in the last nine months, working towards a common goal.

That doesn’t prevent the risk of another pandemic, but we’ve learned to respond more rapidly.