The COVID-19 vaccines, in particular the AstraZeneca vaccine, have dominated the news this last week for a mixture of reasons.
As more evidence emerges for the effectiveness of the vaccines - not only in reducing infections from COVID-19 but also in the transmission rates of the virus – there is much to be positive about. Unfortunately predominantly political controversies around both vaccine procurement and delivery have played out across much of Europe’s press.
This has resulted in different European countries issuing differing approvals for the AstraZeneca vaccine with some licencing it for all adults over the age of 18 (as per the UK and the EU’s own regulatory drug authority guidelines), whilst some are restricting its use in older people and one country, Switzerland, has decided not to give any approval to the AstraZeneca vaccine.
Alongside this is the ongoing debate about just how long the interval between the first and second dose of the Pfizer vaccine should be with some countries, the UK in particular, placing more emphasis on getting as many first doses into people as possible whilst others are preferring to get both doses into a lower number of people.
The unfortunate consequences of all of this is that it can leave people feeling unsure about vaccination and wondering if they can trust the stance their particular country is taking with regards to the vaccine roll-out.
In this piece I will address some of the questions I have been asked this week.
Question: I live in the UK where we are using a lot of the AZ (AstraZeneca) vaccine but how can I be sure it’s safe given the fact so many other countries are not happy to use it yet?
Firstly it is vital to understand that not even countries such as Switzerland (who has not yet approved the AZ vaccine) have said they have any concerns over its safety.
France, Germany, Italy, Sweden, Belgium and Poland have all advised against using the AZ vaccine in older people because they want to see more trial data first.
In the initial phase III trials for the AZ vaccine 12% of recruits were aged 56 and over (the initial trials recruited 11,636 people, 1418 of whom were aged 56 and over.)
Data from ongoing trials of the AZ vaccine in the USA and South America will be available within the next few weeks. These trials have recruited over 30,000 people. (1)
Although some political leaders have made claims that the AZ vaccine is less effective for older people there is no scientific evidence for this claim. There was also some misunderstanding that the vaccine was only 8% effective in the over 65 age group when this was actually the percentage of participants over the age of 65 in the first trials.
In its first trials within a laboratory setting the AZ vaccine was shown to produce a strong immune response in all age groups, including the over 65s.
During this initial laboratory testing phase all participants had regular blood tests to assess the amount of antibodies they were making in response to the vaccine so researchers obtained an extremely accurate picture of what was happening with each individual’s immune system. (2)
Dr June Raine from the UK Medicines and Healthcare products Regulatory Agency (MHRA) said, "The data we have shows that the vaccine produces a strong immune response in the over-65s, and that it is safe."
In later stages of vaccine testing, which involve larger numbers of participants, scientists wait to see how many people go on to catch COVID-19 and, of those who do, how many are in the placebo arm of the trial and how many are in the vaccinated arm.
There were 660 people aged 65 and over in the first AZ vaccine phase III trial and of those only two became infected with COVID-19. Some countries feel that the numbers are too small to be reliable and want to see results from a greater number of older participants.
As Professor Jim Naismith of Oxford University explained “some countries want to see more evidence of its effectiveness in the over 65s before committing to administering it to them.”
Professor Naismith also made the observation that "Scientists often disagree about how much evidence is needed for any new advance and there is always more data to be secured. Normally this all happens out of sight of the glare of the media and not in a pandemic, but such debates are an important part of the scientific process." (3)
The AZ vaccine has now been approved in around 50 countries across four continents.
Question: Why is the UK the only country extending the length of time between having a first and second dose of vaccine?
The UK government decided to change the length of time between the first and second doses of the Pfizer vaccine, increasing it from 3-4 weeks to 10-12 weeks. The reason was to try and give as many people as possible their first dose of vaccine and so benefit a greater proportion of the population. Others have argued that as Pfizer recommended the shorter interval to do anything other than this could interfere with the body’s immune response and perhaps allow the virus to develop resistance to the vaccine.
(Note: The AZ vaccine is always given with a 12 week dose span, it is only the Pfizer vaccine that has had its time scale adjusted in the UK.)
It is important to remember that vaccine trials are planned out within parameters that the researchers think are the “best fit” at the time. A licence for the vaccine, if approved, is then set within these parameters. This happens even if it becomes clear that a different approach with different parameters may have worked better.
When Pfizer began their trial they were expecting an efficacy of around 60% after the first dose and the second dose was expected to increase this to in the region of 80%. In fact, the first dose reached efficacy rates of 89%, much higher than expected. If the researchers had known this would be the case they may have built a longer time interval between doses into their original trials but at the time they could only plan around what they thought the efficacy was most likely to be. (4)
In the UK the JCVI (Joint Committee on Vaccination and Immunisation) takes into account the situation being faced and accrued experience with other vaccines as well as the available trial data.
The JCVI already knew that with other vaccines increasing the time between doses leads to a better immune response. It was able to combine that knowledge with all the available data on the COVID-19 vaccines and plan the best way forward to vaccinate against COVID-19 and save lives. With time we will have increasingly better data on the quality of immunity each of the vaccines produces and it is likely that adjustments to timing of doses may happen again.
Evidence is already emerging that the AZ vaccine is 76% effective from 3 weeks after the first dose and that this immunity lasts for at least 12 weeks. What the AZ researchers had thought was the right dosing interval in theory is now being shown to be true in practice as large scale evidence comes in from all those who have been vaccinated. (5)
The JCVI made its decision to lengthen the time between the first and second dose of the Pfizer vaccine based on its previous knowledge of how other vaccines work, combined with the vaccine data from Pfizer, in the face of an unfolding emergency.
As Professor Deborah Dunn-Walters, the chair of the British Society for Immunology’s Covid-19 and Immunology taskforce, explained “The UK government’s decision to change the timing of the second vaccine dose has been controversial. After all, if you have evidence that scheme A works, why would you use an untested scheme B? But the decision will not have been taken lightly and there is some basis in the current data available. AstraZeneca trials reported early indications that a longer interval between doses is beneficial. Pfizer trials did not have such data, but the similar Moderna vaccine elicited immunity lasting just under two months after one dose. It boiled down to simple sums based on real-world scarcity: if a vaccine protects people from disease by 89% after one dose and 95% after two doses, and someone gives you just 200 doses this month, you can choose to protect 95 people after three weeks or 178 people for 12 weeks."
It is worth noting that Quebec in Canada has also adopted a postponed second dose policy in order to vaccinate more people and that Israel has said they would do the same if vaccine supplies were limited. (6)
Question: There seem to be so many new variants being found at the moment. I am not going to get vaccinated yet, I am going to wait until there’s a better vaccine that works on those variants too.
It is essential that as people are called for vaccination they go and get their jab. Delaying your vaccine will keep both you and the other people around you at a higher risk of catching COVID-19. Even if the vaccines are less effective against some of the new variants that is not a reason to not be vaccinated.
As Professor Adam Finn from the JVCI said in interview, “It may be the case that they are just slightly less efficient than they are against the initial Wuhan virus, but that doesn’t mean they are not useful. These vaccines are much more effective than we dared to hope in the first place so some reduction in their efficiency is not a disaster.”
And Dr Michael Osterholm, an infectious disease expert from the University of Minnesota, said "At this point, there is no evidence that these variants have changed the equation in terms of protection from the vaccine but we have to be prepared for that." (8)
All the main vaccine companies are already working on potential changes they may need to make to their vaccines in the face of lower efficacy against the virus. The fact we have to change the flu vaccine each year means that the concept of altering or adapting a vaccine for a new strain is something scientists are already very experienced in.
If people hold back from taking the current vaccination it is highly likely that COVID-19 infections will start to climb again when lockdown is eased. This in turn not only means more COVID-19 deaths but continues to provide the virus with opportunities to circulate and mutate again and again.
Delaying your vaccination in the hope that a future one will in some way be better than the current one is flawed logic. It is like a drowning man refusing the first life buoy thrown his way because a better one may come his way a little later. Indeed it might....but by then it would be too late for him.
(2) https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)32661-1/fulltext#seccestitle200
