Covid-19: Will the vaccine protect me from Omicron? – Stuff.co.nz

As Omicron continues to proliferate at astonishing rates, Keith Lynch explains that Covid-19 vaccines very much do work against the new variant.

I'll get right to the point. Yes, the vaccines work against Omicron. Its just that they arent necessarily doing what wed love them to do.

Among the key reasons the variant is spreading so fast is that its excellent at evading some of the protection against infection we have gained by getting vaccinated or by having previously had Covid-19.

That does not mean the vaccines have failed, however. In fact, one of the key reasons why Omicron appears to be less severe than Delta is precisely because of all those vaccinations.

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Think of these as your first line of defence.

Thats not the only protection we have after vaccination. As Dr Fran Priddy, clinical Director of Vaccine Alliance Aotearoa New Zealand, previously told Stuff; the body also makes whats called B and T cells. This layer of protection is called cellular immunity.

This response is more robust and long-lasting. The B cells can pump out new antibodies when needed, and T cells kick into action once the virus makes its way past that first line of infection.

We learned last year, however, that Covid-19 antibodies diminish over time. Youll have seen this described as waning immunity. This is perfectly normal, by the way.

What it meant, though, was that the virus was able to take root in immunised people as that first line of defence wasnt necessarily as strong as immediately after vaccination.

But remember those T and B cells are still there ready to go. They step up and prevent most vaccinated people getting severely ill after contracting Covid-19.

Omicron is a highly mutated version of Covid-19, but its still Covid-19. Most of its mutations are on a part of the virus called its spike protein.

The antibodies our first line of defence typically bind onto the spike protein in an attempt to stop the virus taking hold.

Vaccinated peoples Covid antibodies are having a tough time, though, with Omicrons change-up.

But again, its not just about antibodies. The good news, as Professor Paul Hunter of the University of East Anglia explains, is that there are very few mutations on the parts of the virus targeted, for instance, by T cells.

And while Covid-19 has mutated, it can only change so much, Priddy says. Also, those T cells are much better at targeting the parts of the virus that, broadly speaking, stay the same.

Indeed, a recent study from scientists in Hong Kong and Melbourne support this. While the number of infections may rise considerably as a consequence of Omicrons ability to evade antibodies, robust T cell immunity provides hope that, similar to other VOCs (variants of concern), the level of protection against severe disease would remain high, the authors wrote in an article published in the Viruses journal.

OK. Number one: a third dose will bring about a new wave of eager antibodies that will reduce the chances of you catching Omicron (and Delta) in the first place.

Thats not all. A booster will also induce a process called affinity maturation, Priddy explains. This essentially means after repeated exposure to the vaccine (or indeed the virus) the immune system improves itself. It becomes more refined and better able to fight back.

Dr Nikki Moreland, an Associate Professor in Infection and Immunity at the University of Auckland, equates this to studying something complicated.

When you read something the first time around, you kinda know whats going on. You read it again and your understanding improves. Then you read it for a third time and you really get it.

One question for immunologists is: how many doses will be needed in the long term?

And there may well be diminishing returns, Priddy says. A lot of childhood vaccines, for instance, involve three doses five or six arent necessary.

Well start with the bad news.

For the reasons Ive outlined above, two doses of the Pfizer vaccine offers less protection against symptomatic Omicron than with Delta, according to data from the UK Health Security Agency (UKHSA).

Their January 6 technical report suggests that in those first few weeks after a second dose, the vaccine is about 60 per cent effective at halting mild illness.

Theres a temporal aspect to this, too. That number drops after three-or-so months as the antibody numbers wane.

A booster certainly appears to ramp up protection from symptomatic illness, at least in the short term, as you see the dataset below.

Thats not to say the vaccines wont stop some Omicron infections. The new variant is just more likely to get around our first line of defence.

A recent Danish study (yet to be peer-reviewed) supports these findings, suggesting that Omicron is much more adept at evading the protection the vaccines offer against infection.

The researchers wrote: Our findings confirm that the rapid spread of the Omicron VOC primarily can be ascribed to the immune evasiveness rather than an inherent increase in the basic transmissibility.

Theres another thing to consider here: If youre exposed to Omicron, theres a chance you could end up being infected with Covid-19 but have no symptoms.

Another South African study (also yet to be peer-reviewed) suggests that Omicron causes more asymptomatic cases than the other variants.

This high prevalence of asymptomatic infection is likely a major factor in the widespread, rapid dissemination of the variant globally, even among populations with high prior rates of SARS-COV-2 infection, the researchers noted.

All of this helps explain its alarming spread.

Philipp Schulze/AP

Sheep and goats stand together in Schneverdingen, Germany, as they form an approximately 100-metre long syringe to promote vaccinations against Covid-19.

And now to the good news.

It appears, so far at least, the proportion of cases ending up in the ICU or dying with Omicron is lower than with previous variants. This is likely a product of a few things: Omicron being less severe and the immunity accumulated via vaccination and prior infections.

Another UKHSA analysis has found the risk of someone being admitted to hospital with Omicron was approximately one-third of that for Delta. This analysis took into account a range of factors including age and vaccination status and points to an inherent reduction in the new variants severity.

A further examination (combing all vaccine brands) offers an indication of how well the vaccines prevent severe illness from Omicron.

It suggests that vaccine effectiveness against hospitalisation for three doses is about 88 per cent. (Key takeaway: boosters work.)

It also notes:

Lets take a breath here. This looks far from ideal at first glance; with Delta, two doses of Pfizer offered higher protection against hospitalisations. Three doses was even better.

But remember, Omicron appears intrinsically less severe. Even if you were not vaccinated, youd have less chance of ending up in hospital compared to Delta. Were working from a different baseline.

Vaccination, particularly a third dose, then further reduces the chances of you ending up in hospital or ICU.

These findings are supplemented by data from South Africa which shows two doses of the Pfizer vaccine is 70 per cent effective against hospitalisation with Omicron.

Encouraging new data from over the weekend also suggested that after three doses, protection against hospitalisation stays close to 90 per cent for people aged 65+ for at least three months or so.

Yes, it looks like it.

Dr Stephen Kissler, an infectious disease expert from Harvard University, said researchers were still waiting more on Pfizer-only epidemiological data, but early signs were encouraging.

South Africa saw far fewer deaths relative to cases probably because so much of the population had immunity from prior Delta infections, he said.

If Delta infection protected against severe Omicron disease, there's good reason to hope that the Pfizer vaccine would do the same.

He also points to Israel, which like New Zealand, is heavily vaccinated with Pfizer (although with far more boosters in arms). Cases are on the rise in the country, deaths are not.

It may still be too early to see much variation in deaths there, since theres such a lag between cases and deaths, but still the fact that were not really seeing anything so far is encouraging, Kissler said.

Pulling from a range of international sources, Professor Paul Glasziou of Bond University in Australia, outlines a scenario that suggests for those who have had at least two doses the chances of dying from Omicron are likely similar to the flu.

In the unvaccinated, the outcomes are significantly worse.

The problem with Omicron, as he notes, is that it creates so many cases so quickly. In well-vaccinated countries ...Omicron seems to be like having months of flu season compressed into a couple of weeks, swamping health care.

This is why the virus is causing such problems in Britain and Australias New South Wales.

And, of course, there are still plenty of unvaccinated people still out there.

I know. It is summer and case numbers are low in Aotearoa. You probably remember, though, all that discussion about Delta being able to find those vulnerable unvaccinated pockets.

By and large, so far, that hasnt happened. The incredibly high vaccination rates across New Zealand have seemingly helped keep Delta in check.

But as I have explained, Omicron is less likely to bounce off the vaccinated. Its incredibly good at hitching a ride on vaccinated people and going on to infect others who have absolutely no protection.

Indeed, a recent UK report notes: The percentage of patients admitted to critical care with confirmed Covid-19 that were unvaccinated decreased from 75 per cent in May 2021 to 47 per cent in October 2021, consistent with the decreasing proportion of the general population who were unvaccinated, before increasing again to 61 per cent in December 2021.

Theres other data below that shows the dramatic reduction in risk in the vaccinated.

The optimistic take here is that after the Omicron variant washes through a population, theres a huge boost to the collective immunity.

New Zealand epidemiologist Tony Blakely has talked about allowing a manageable number of Omicron cases, suggesting: If everyone is going to be exposed to Covid-19 at some point (which seems likely), then it would make sense for those who refuse to get vaccinated to take their chances with Omicron; the next variant may be more virulent again.

This piece isnt about debating the merits of this argument. There would clearly be huge costs associated with a huge Omicron surge in New Zealand. And there are obvious concerns about long-term implications of infection.

But Ill try to answer this question as best I can: would an Omicron infection (assuming the person survives, obviously) provide an extra layer of protection?

Theoretically yes, Priddy told me. But there are, of course, a lot of unknowns.

Hold on, you might say! Ive read that mid-December report from the Imperial College in London that found that the risk of people who had already had Covid-19 getting reinfected with Omicron was 5.4 times greater than that of the Delta variant.

I also spent Christmas reading that South African study that suggested that Omicron can indeed escape the immunity that people who survived Delta had.

Remember though, there are two things at play here: protection against infection and protection against severe disease.

MONIQUE FORD/Stuff

People in Wellington queue for vaccine boosters.

Throughout the pandemic, previous infections have appeared to offer protection against severe disease. In a recent letter to the New England Journal of Medicine, citing data that pre-dates Omicron, Qatar experts wrote: Reinfections had 90 per cent lower odds of resulting in hospitalisation or death than primary infections. (This study only included unvaccinated people).

The authors added: It needs to be determined whether such protection against severe disease at reinfection lasts for a longer period, analogous to the immunity that develops against other seasonal common-cold coronaviruses, which elicit short-term immunity against mild reinfection but longer-term immunity against more severe illness with reinfection.

A Swedish study also suggested that the T Cells induced by both prior infection or vaccination hold up well against Omicron.

Moreland also explained that yes, theoretically, hybrid immunity that is someone who has been vaccinated and had the virus should have a more robust immune response in the future.

But what happens if a brand-new variant arrives? Will it just ignore everything that has gone before? It could happen, but its unlikely.

In a Twitter thread this week, Professor Francois Balloux, the director of University College Londons genetics institute, wrote: No variant can become totally impervious to vaccines and boosters and protection from prior infection. A variant can largely escape 'neutralising antibodies' as Omicron does, and thus be more prone to (re-)infect immunised hosts.

Kissler agrees with this take. We're very unlikely to get a new SARS-CoV-2 variant that totally evades all of our immunity. Our T-cells, in particular, are basically engineered to keep up with pathogen variants.

Moreland says the same. While she acknowledges there are no certainties, a variant thats so novel it completely evades vaccines does not seem plausible.

The virus needs to get into our cells to cause infection. The changes needed to totally escape our immune response would be huge, I doubt it would then be able to enter our cells.

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Covid-19: Will the vaccine protect me from Omicron? - Stuff.co.nz