As you are aware the UK was the first place to approve COVID-19-related vaccinations in late 2020. Vaccines were made so fast because the virus was identified and the sequence was given to the World. This is known to some a Wuhan strain or the A strain or the Index Virus. The first major variant to surface in the UK was called the UK/Kent strain but was given an offical number B.1.1.7. It was given the name alpha, Whilst other variants were circulating in South Africa (Beta) and South American (Gamma). The SARS-CoV-2 vaccines were based on the Index strain sequence and this produced antibody lasting about 6 months in terms of protecting against infection and probably life-log immunity. To stop infection you need a certain level of antibodies that can swamp the virus as it infects and so prevents clinical disease.
The protective levels remained high for a few months but because we were isolating/shielding we were not encountering any natural virus, so immune system thinks job done, shut down production. So with time your protective immunity disappeared and so you could get infected before you can make new and enough antibody to deal with infection.
The next strain to hit the UK was delta. Whilst it was more infective than the original strain, the vaccine response was pretty effective, but you needed a slightly higher level of antibody to protect against it. Hurray and most of the UK was vaccinated and booster and infection rates and deaths dropped in the vaccinated majority.
So as we were patting ourselves on the back, the virus had other plans and it mutated to develop immune-escape meaning that you need alot more antibody to stop it infecting. We had seent this with beta and gamma…but omicron took this to a whole new level. This had loads and loads of mutations compared to what had gone before….mutation in an immunosuppressed individual that couldn’t clear the virus or maybe a species evolved in animals that jumped back to humans.
Now it meant we didn’t need a doubling of antibody levels to stop infection we needed 10 or 20 or hundred times the wuhan-directed antibody level to give infection. Because the antibodies were waning with time the level required to stop infection soon was lost and so the protective effect of vaccination lasted a few weeks as a consquence most people vaccinated with Wuhan developed COVID-19 in 2022 due to infection with omicron. As BA.4. and BA.5 became dominant the vaccine was alot let efficacious
So now we have a new vaccine, which will boost the response to the Wuhan strain but will give protection against omicron. Therefore it should mean that the level of antibody required to stop infection will be lower as we will now make antibodies specific for omicron. This is why it is a good idea to get a boost with the new omicron COVID-19 vaccine.
In addition, things have changed and we are now “out and about” and this means we will encounter omicron or whatever comes next. This means we will get sub-clinical infections because we are getting infected whilst we still have a vaccine response, this gets rid of the infection but gives you a boost. so your antibody levels will increase again. If this happens repeatedly you can develop high levels of protective antibodies that give you long-term protection
Sadly for MS, people taking fingolimod, ocrelizumab and rituximab did not make a good antibody response increasing infection risks. This was partially countered by booster doses that increased the antibody response in people making a response and increased the proportion of people making a response. For anti-CD20 the capacity to respond related to the therapeutic antibody levels and the B cell counts, which have a relationship between CD20-depletion and vaccination.
The antibody responses were increased in fingolimod and anti-CD20 took a break, but given that disease can return many consider this an unacceptable risk, but in rheumatoid arthritis and cancer they have formally tested the “treatment breaks” with immunosuppressive drugs and it can work. Likewise increasing the number of boosters help some individuals make a response.
I will be waiting to get my boost, don’t forget to do your bit for Society…it is not about you! It is about protecting the populaton. The newly approved vaccine will target BA.1 omicron, another version targeting BA.4/BA.5 is a month or more behind the one approved today. Will the UK get to approve this first too.
Disclaimer. These are my views and my diagrams created with Biorender.