While government is reportedly moving from pillar to post in a hastened move to source vaccine against Covid-19, empirical studies are showing that there is nothing much to celebrate or to be excited about with the coming of the much-awaited doses.
Other than the fact that emaSwati have received devastating news that government has abandoned its initial plan of procuring the Oxford/AstraZeneca vaccine amid concerns that it is not effective to the new South African variant, there are other numerous reasons that make the news of the yet to be sourced vaccine not exciting at all.
Findings of a couple of studies done by the vaccine producers themselves and other health institutions have shown that getting the vaccine will not be a guarantee that the country will get out of the woods. The crosscutting findings which paints a gloomy picture even after the vaccine rollout include but not limited to thatalmost all the vaccines produced so far doesn’t provide 100 percent protection against contracting the deadly coronavirus, there is no evidence as yet that having had the vaccine will stop you getting the virus and passing it on, most of the vaccines start to be effective after 14 days, which means one can contract the virus after vaccinating and almost all the vaccines will require that each person get two doses because the chances of protection remain low if one has got one dose.
At the time of writing this story, over 616 people had died of Covid-19 related complications, 16,341 confirmed cases and 11,955 had recovered.
vaccines require booster doses to work
In fact, most vaccines require booster doses to work.
Take the MMR – measles, mumps and rubella – vaccine, which is given to babies around the world to prevent these deadly childhood infections. Around 40 percent of people who have received just one dose are not protected from all three viruses, compared to 4.0 percent of those who have had their second.
People in the former group are four times more likely to catch measles than those in the latter – and there have been outbreaks in places where a high proportion of people have not completed the full MMR vaccination schedule.
“The reason that people are so keen on boosters and consider them so vital is that they kind of send you into this whole other kind of fine-tuning mode of your immune response,” says Danny Altmann, professor of immunology at Imperial College London.
How booster vaccines work
When the immune system first encounters a vaccine, it activates two important types of white blood cell. First up are the plasma B cells, which primarily focus on making antibodies. Unfortunately, this cell type is short-lived, so although your body might be swimming in antibodies within just a few weeks, without the second shot this is often followed by a rapid decline.
Then there are the T cells, each of which is specifically tailored to identify a particular pathogen and kill it. Some of these, memory T cells, are able to linger in the body for decades until they stumble upon their target – meaning immunity from vaccines or infections can sometimes last a lifetime. But crucially, you usually won’t have many of this cell type until the second meeting.
The booster dose is a way of re-exposing the body to the antigens – the molecules on pathogens that trigger the immune system – to initiate part two of the response. So, once you’ve had your boost you’ll have a higher frequency of memory T cells and ditto to some extent for the size of the pool of memory B cells you’ll have. They’ll also be making higher quality antibodies.
On second exposure to the same vaccine or pathogen, the B cells that remain from before are able to rapidly divide and create a menacing throng of descendants, leading to a second spike in the amount of antibodies circulating.
The second dose also initiates the process of “B cell maturation”, which involves selecting the immature ones with the best receptors for binding to a particular pathogen. This happens while they’re still in the bone marrow – where white blood cells are made – and afterwards they travel to the spleen to finish developing. This means B cells are not only more numerous afterwards, but the antibodies they produce are better targeted.
Memory T cells, meanwhile, also proliferate rapidly. They are already thought to have played a critical role during the current pandemic, protecting some people from developing severe Covid-19. Though the virus may have only been circulating globally since around December 2019, there is some evidence they may have “seen” other coronaviruses before, such as those that cause the common cold – allowing them to recognise Covid-19.
So how effective is a single dose of each of the Covid-19 vaccines?
At a time when the answer is more urgent than ever – especially as the British government has decided to delay the second dose of all currently approved Covid-19 vaccines from 3-4 weeks to 12, and Russia is trialling a single-dose regimen of its Sputnik V vaccine named “Sputnik-Light” – it is also surprisingly complicated. Here’s what we know from studies.
According to Pfizer data published in December 2020, the Pfizer-BioNTech vaccine is roughly 52 percent effective after the first dose. Out of 36 523 participants in the phase three trial – the final stage of testing where people either received two full doses, 21 days apart, or a try-on group – who had no evidence of existing infection, 82 people in the try-on group and 39 in the vaccine group developed Covid-19 symptoms.
However, studies revealed that this early protection comes with some important caveats. First, the protection doesn’t kick in until at least day 12 – until then, there was no difference between the two groups. Secondly, one dose is still significantly less protective than two. The latter is 95 percent effective at preventing the disease after a week.
But there is also another figure that has been circulating on the internet, and anecdotally, being fed to patients by certain doctors – the suggestion that the first dose is around 90 percent effective.
The second estimate comes from the UK’s Vaccine Committee, the JCVI, who decided to calculate the efficacy of the vaccine differently. Instead of using all the data on the number of infections, including from days when the first dose hadn’t yet started to work, they only looked at days 15-21. Using this method, the efficacy of the vaccine jumps up to 89 percent, because it’s not being diluted by the relatively high number of infections before the vaccine begins to have an effect. Taking things even further and only looking at the first seven days after the second dose (days 21-28) – because the second dose might not have kicked in yet by then – it’s 92 percent.
In a more recent development, an Israeli academic who coordinated the country’s Covid-19 response – Professor Nachman Ash – has claimed that a single dose of the vaccine is not as effective as Pfizer originally estimated. However, the comments have been widely criticised.
For one, the Israeli study found that a single dose of the vaccine reduced the number of people testing positive for the virus, i.e. being infected, by 33 percent, while the Pfizer paper suggested that it would prevent 52 percent from developing symptoms – they looked at two different things.
For the Oxford-AstraZeneca vaccine, things are a bit different. In a paper published in January, the authors explain that the vaccine offers protection of 64.1 percent after at least one standard dose. This compares to 70.4 percent if you’ve had two full doses, or – oddly – 90 percent in people who have had one half dose followed by one full dose.
Meanwhile, based on these unpublished data they have seen, the Vaccine Committee has estimated that, from three weeks until 9-12 weeks after the first injection, the vaccine prevents around 70 percent of cases of serious disease.
According to a document the company submitted to the FDA, the Moderna vaccine can provide 80.2 percent protection after one dose, compared to 95.6 percent after the second (in people aged 18 to 65 – it’s 86.4 percent in those over 65). As with the Pfizer vaccine, all participants in the phase three trial received two doses of the vaccine or a placebo within a single set time period – in this case, 28 days – so it’s not yet known whether the immunity from a single vaccine would continue, or drop off after this stage.
The CoronaVac vaccine was developed by Sinovac, a biopharmaceutical company based in Beijing, China. This version is unusual as it has been trialled independently in several countries – all of which have produced different results.
According to researchers in Turkey, the vaccine is 91.25 percent protective, while scientists in Indonesia have said that it’s 65.3 percent effective, and the Butantan Institute in São Paulo, Brazil recently announced that the vaccine prevents 50.4 percent of people from developing symptoms. At the moment, no one has released data on the efficacy of a single dose – these figures only apply to two doses, spaced 14 days apart.
The results have been viewed with some scepticism, because they were published via press releases, instead of – as would normally be the case – in a peer-reviewed journal. Without access to more information about the trial methods and the data that was collected, it’s harder for scientists to make their own assessments of the results’ validity.
In all, there are five Chinese vaccines at various stages of development.
Another is “BBIBP-CorV”, by the state-owned company Sinopharm, based in Shanghai. Officials in the country recently announced that this version is 79 percent effective after two doses – though by then, it had already been distributed to nearly a million people. This estimate has not been verified by the international community, because the underlying data and methods for its trial have not been made publicly available. It’s not yet clear how protective it might be after a single dose.
Outside China, the vaccine is currently being tested all over the world, and has been approved in Bahrain, Egypt, Jordan, the Seychelles, and the United Arab Emirates. The UAE recently became the first to rate its efficacy, claiming via a press release that it is 86 percent effective.
The Sputnik V vaccine is named after the world’s first artificial satellite, the iconic Soviet-era “Sputnik 1”, which was launched into low Earth orbit in October 1957 – it burned up three months later when its batteries died. Its namesake was developed by the Gamaleya Research Institute of Epidemiology and Microbiology in Moscow, Russia.
As with the others, this vaccine is administered as two doses, and is apparently 91.4 percent effective after both – there is currently no publicly available information on the efficacy of just one dose.
Again, these results haven’t been published in a peer-reviewed journal and therefore may not be reliable. Despite a rapid rise in the number of Covid-19 cases in the country, the vaccine’s safety and efficacy has been viewed with suspicion by many Russians, according to a report in the Washington Post. In the first week it was rolled out in December, clinic waiting rooms were reportedly half-empty.
More recently, the Russian government announced that it was developing a new version, “Sputnik-Light”, as a temporary solution to shortages of the original. The vaccine would be delivered as a single dose, though it’s not yet clear how protective it would be.
Can you change your behaviour after receiving a single dose?
Health experts are of the view that they would behave exactly as if they hadn’t had the vaccine yet. They wouldn’t drop their guard at all or do anything differently.
Deborah Dunn-Walters, professor of immunology at the University of Surrey, was just as unequivocal about how people should behave. “There’s a couple of reasons for that,” she says. “One is, you’re not going to be fully protected. And another is there is no evidence as yet that having had the vaccine will stop you getting the virus and passing it on.” The University of Surrey is a leading university located within the county town of Guildford, Surrey in the South East of England, UK.
Dunn-Walters explains that the efficacy of the vaccines were largely assessed by looking at whether they prevented people from developing symptoms – not if they stopped them being infected with the virus. “And we do know that it’s possible to have asymptomatic infection,” she says. There is not yet any evidence that one dose – or even two – of the existing vaccines will stop people from giving the virus to others.
Can you skip the second vaccine dose?
Experts say preclinical trials would have shown that they didn’t think there was enough immunity after one shot, so they’ve gone for both. Similarly, they concur, during phase three trials, there were more antibodies and T cells in the blood after two doses than there were after one.
As the Chief Executive of Pfizer, Albert Bourla, explained in December that it would be a “big mistake” to skip the second dose, because it almost doubles the amount of protection you get.
Pfizer and BioNTech themselves have already urged caution on the grounds that their data ends at day 21, and “there is no data to demonstrate that protection after the first dose is sustained after 21 days”. It’s possible that the protection people seem to have will suddenly drop off after that point – in fact, this wouldn’t be surprising based on the way the immune system usually works.
Reliably estimating how long the protection from a single dose might last is further complicated by the fact that all the currently approved Covid-19 vaccines are using brand-new technology.
The Oxford-AstraZeneca and Sputnik-V vaccines both involve modified versions of adenoviruses – a group that can break into many different cell types and cause a range of illnesses, such as respiratory infections. While the Oxford version uses an adenovirus from chimpanzees, the Russian one includes a mixture of two human types.
Experts found that the virus was altered for the vaccines so that it’s safe and can’t make more copies of itself inside cells. It is able to teach the body to recognise the coronavirus by encoding the instructions to make a feature found on its surface, the spike protein.
Immunity takes time to develop
Finally, Dunn-Walters is keen to point out that immunity takes time to develop – so regardless of whether a single dose of any of the Covid-19 vaccines can provide protection eventually, for the first couple of weeks you will have no more than you started with.
“There’s a part of the immune system which we call innate immunity, which responds immediately,” says Dunn-Walters. This encompasses physical barriers to infection, like your skin, as well as certain types of white blood cell and chemical signals. But she explains that this generally can’t prevent disease on its own – and isn’t affected by vaccines. “So you need adaptive immunity as well. But the issue with adaptive immunity is that, as its name says, it’s adaptive – it adapts to individual challenges by pathogens.”
For vaccines to have any effect, they must encourage the body to make more immune cells – some of which in turn produce antibodies. “And this takes time,” says Dunn-Walters.
So while the global roll-out of the new vaccines may be exciting, it looks like most of us will have to wait a while longer before normal life can resume.