Shared this on another thread, it's a good explanation of why the change to the vaccine schedule is actually a good thing, but has been incredibly poorly communicated. It's from Tom Fardon who is worth following on Facebook.
Happy New Year. Vaccine Chat.
A number of people have asked me about the vaccines in the last 4 weeks, particularly in the last week since the guidance on dose intervals has changed: the 4 chief medical officers now recommend that the vaccines are not given at a 4 week interval now, rather they are given 8 to 12 weeks spaced apart.
This is good news in a number of ways. The most important practical thing is that there are only a limited number of vaccines available to give, so from the start of December whenever anyone got a vaccination, their second dose had to be put aside to give to them a month later. Now we can use those 'second doses' to vaccinate more people for the first time - more people vaccinated at all is a good thing.
Vaccines work by generating an immune response to a foreign antigen, in this case COVID proteins (either generated by transcribing injected mRNA, or spliced onto some simian adenovirus), leading to production of antibodies (easy to measure) and memory T cells (hard to measure).
After the first vaccine shot there are detectable antibodies at 28 days - the table below is from the UK Govt website (https://www.gov.uk/government/publications/regulatory-approval-of-covid-19-vaccine-astrazeneca/information-for-healthcare-professionals-on-covid-19-vaccine-astrazeneca) - the figure is 7,000-8,000 if you care about the numbers. This is comparable to the figures found in people who have had COVID.
28 days after the second shot there are more detectable antibodies - more than 20,000. But if you look at the table, the response actually goes up the longer the interval between the vaccinations: 22k at < 6 week interval; 24k 6-8 weeks; 34k 9-11 weeks; and 63k when the interval is ≥ 12 weeks. There's a rationale for this - the complete immune response is probably not complete until 6 weeks post vaccination; the simian adenovirus vector generates an immune response too, but it wanes so leaving the second vaccination longer means less simian adenovirus antibody, so more exposure to the vaccine, and a bigger COVID antibody response.
Longer dosing schedules lead to improved responses in other forms of vaccine too. The graphs below show that flu and ebola vaccinations generate better antibody responses when given at longer intervals, using a variety of vaccination mechanisms, not just adenovirus vectoring. So although we only have the longer dose interval data for the Oxford/AZ vaccine, not the Pfizer vaccine, there isn't a very good rationale for why the response would be any different.
So is the 7k-8k of antibodies after the first injection "enough". The next graph shows the difference between getting one placebo vaccination and one actual vaccination, in terms of getting COVID - the lines diverge between 7 and 14 days, suggesting that however many antibodies, or T cells, or whatever bit of the immune system is generated, it happens within those first 2 weeks.
The upshot of all this is, if you've had your first vaccine and have just found out that your second vaccine due next week has been postponed, it's good news for someone else who is going to get that vaccine instead, and good news for you that you'll probably be better protected from the booster by having it 8 to 12 weeks later, not 4.
(Here's a great Twitter Thread about all of this from an actual vaccine researcher in Oxford - I have used a lot of his chat in here, you can read his thoughts directly here: https://twitter.com/sandyddouglas/status/1344949258483621888)
Another recent change to the vaccination advice was that the vaccines can be given to people who have food and other allergies. This is another good thing, allowing more people access to the vaccines.
The list of ingredients in the vaccines is very small. The Ox/AZ vaccine has the viral component, then the list of excipients below. L-Histidine is an amino acid, we get it from food, and need it for nerve function. Polysorbate 80 is a plant based surfactant and emulsifier. Ethanol is an alcohol. Sucrose is a sugar. Sodum chloride is table salt. Disodium edetate dehydrate (EDTA) is a chelating agent (it pulls metals out of solution), is found in food, and is at such a low level in this vaccine (less than 1mmol per dose) that it is considered essentially sodium free. Certainly nothing toxic, nothing dangerous, and nothing that hasn't been used before in injectable form.
Other key vaccine snippets:
Both of the vaccines simply present SARS-CoV-2 proteins to the immune system.
There is no live (or dead) virus within either vaccine.
Neither can possibly give the recipient COVID.
The Pfizer vaccine contains mRNA: it does not, and cannot, alter host DNA.
Will the vaccine protect us against new strains? Most likely. The protein antigen in the vaccine is large (in terms of proteins, at least) - the mutations are in only small areas of this large protein. The immune system generates antibodies against lots of parts of the protein, not just the bits that have not been mutated. A good analogy is this - you can recognise your best friend whether they are wearing a hat, or not; the immune system, once primed with the vaccine, will recognise SARS-CoV-2 proteins, just not the bits wearing the hat.
The messages from colleagues in the larger cities in the UK, particularly London, are that there has been an exponential increase in cases and admissions to hospitals. Some London hospitals report there are more patients with COVID that with everything else put together, and 94% of these are cases admitted from the community (only 6% have become COVID positive since being admitted with something else).
What we can do about it is the same as we've been doing so well with over the last 8 months - face coverings, avoiding crowded places (particularly indoors), hand hygeine, social distancing, sticking with it. People infected can be infectious before having symptoms, so don't assume you or anyone else doesn't have it. The vaccine roll out has started, and is accelerating, helped by the new dosing schedule, but we have to dig in and stay the course until there's enough vaccination done. That will take many months, but it will happen. Time to double down.