Tuesday, 1 December 2020
Why no vaccine can ever be 100% effective: Wide variation in the population's immune systems mean guaranteed protection is impossible
The announcement of not one but three coronavirus vaccines has been widely welcomed, in particular, their effectiveness.
Preliminary results of clinical trials into the three jabs show their effectiveness — how good they are at stopping people from getting Covid symptoms — varies from 62 per cent to 95 per cent.
The news that none of them reported 100 per cent might sound perplexing. But, the fact is, no vaccine does. Indeed, experts believe the new coronavirus jabs may offer better protection than many other vaccines.
![The three coronavirus vaccines that have recently reported results with effectiveness rates of up to 95 per cent are actually high compared with some vaccines; the flu jab, for example, is only 50 per cent effective on average [File photo]](https://i.dailymail.co.uk/1s/2020/11/30/17/36275592-9002315-image-a-74_1606758718673.jpg)
The three coronavirus vaccines that have recently reported results with effectiveness rates of up to 95 per cent are actually high compared with some vaccines; the flu jab, for example, is only 50 per cent effective on average [File photo]
‘Seventy or 90 per cent effectiveness is remarkably high,’ says Dr Andrew Preston, a reader in microbial pathogenesis at the University of Bath.
‘It means nine out of ten vaccinated people would not become ill with Covid-19 if they were exposed to it.
‘The vaccine may not stop the person catching the infection, but it would stop them getting symptoms of the disease if they caught it.’ But why can’t a jab offer full protection, and does it matter?
Vaccines work by creating a ‘memory’ of the disease should the immune system come into contact with it again — it recognises the disease and triggers a ‘bigger and longer-lasting response’, which means it doesn’t have a chance to take hold and cause symptoms, explains Will Irving, a professor of virology at the University of Nottingham.
‘When developing any vaccine, clinical trials are carried out to find out whether it is effective and if it is, how good it is,’ he explains.
‘To do this you have a group of people that’s vaccinated and another that isn’t, the placebo group. You then count the number of cases of the disease in each group over a period. If you have 25 cases of disease in the vaccinated group and 50 cases in the placebo, the vaccine is 50 per cent effective — i.e. it has prevented half the people in the vaccinated group from getting the disease.’
![Preliminary results of clinical trials into the three jabs show their effectiveness ¿ how good they are at stopping people from getting Covid symptoms ¿ varies from 62 per cent to 95 per cent [File photo]](https://i.dailymail.co.uk/1s/2020/11/30/17/36275552-9002315-image-a-75_1606758725173.jpg)
Preliminary results of clinical trials into the three jabs show their effectiveness — how good they are at stopping people from getting Covid symptoms — varies from 62 per cent to 95 per cent [File photo]
However, while a 100 per cent effective vaccine is the goal, it is impossible to achieve because human make-up differs so much.
The three coronavirus vaccines that have recently reported results with effectiveness rates of up to 95 per cent are actually high compared with some vaccines; the flu jab, for example, is only 50 per cent effective on average.
In comparison two doses of the measles, mumps and rubella (MMR) jab will protect 99 per cent of people from measles and rubella and 88 per cent against mumps; while the whooping cough vaccine is initially 80 per cent effective, protection drops to 60 per cent after four years, reported the Canadian Medical Association Journal in 2016 — which is why children have booster jabs.
‘There is too much variation in the population’s immune systems for any vaccine to be 100 per cent effective,’ says Dr Preston. ‘For example, as we age, our immune system responds less well, which means vaccinating older people in general is a problem.
‘That’s why the flu and pneumonia vaccines, which are largely aimed at older people, contain adjuvants — compounds that boost the immune response to the vaccine, meaning we are more likely to produce antibodies and be protected.’
Any condition that weakens the immune system, including obesity, may also affect our response to a vaccine.
‘Obesity creates an inflammatory state in the body and it’s thought the heightened inflammatory state may exhaust the immune system, making it less able to respond to vaccines,’ explains Dr Preston.
Vaccination won’t just stop symptoms in the individual — it can also stop the disease circulating.
For example, if more than 90 per cent of people are vaccinated with the MMR jab, this reduces the amount of circulating disease, also protecting those who are not vaccinated — so-called herd immunity. Ultimately, this can lead to a disease being eradicated, as happened with smallpox (the jab was 95 per cent effective).
Exactly how many people need to have a Covid vaccine to create herd immunity is unclear; it depends on how infectious the disease is — the ‘R’, or reproduction rate — and how effective the vaccine is.
‘If measles vaccination rates drop below 90 per cent, for ex-ample, there are outbreaks of the disease because measles is fantastically infectious, with an R of around 15,’ says Professor Irving, explaining that SARS-coV-2 (the virus that causes Covid infections) has an R rate of up to 3.
It’s also not clear whether the one in ten who are vaccinated against Covid-19 and yet to show symptoms would be more severely ill if they hadn’t had the vaccine.
Another unknown is whether being vaccinated will stop people from being infectious, so called sterilising immunity.
‘All vaccines are designed to stop the disease they are targeted against, but it is very difficult to generate immunity that actually stops infection,’ says Dr Preston.
‘So no matter how many people are vaccinated, the virus will still circulate. This is the case with the whooping cough vaccine.
‘It stops the Bordetella pertussis bacterium infecting the lungs, which causes this dangerous disease, but it doesn’t stop people from becoming infected in their upper airways, and these people can still transmit the infection.’
Until we have more answers, science has to be transparent, says Dr Preston. ‘No medicine is without risk and we need to be honest about that while at the same time fighting disinformation,’ he says.
Chinese Lehigh University chemistry student, 24, faces prison and deportation after admitting he tried to poison his roommate with a chemical once used in rat poison
A former Lehigh University chemistry student on Monday admitted poisoning his roommate's food and drink with a toxic heavy metal substance previously used in rat poison.
Yukai Yang, 24, pleaded guilty to attempted murder. Under the terms of the plea agreement, the Northampton County District Attorney's Office will withdraw other charges in two separate cases against Yang.
Yang, a chemistry major from China, acknowledged he purchased thallium in March 2018 and began giving it to his roommate, Juwan Royal.
Yukai Yang, 24 (left), has pleaded guilty to attempted murder for poisoning his roommate Juwan Royal (right) with a toxic heavy metal called thallium for three months in 2018
Royal testified in an earlier court hearing that he suffered weight loss, headaches and nausea. He likened the pain from the poisoning to being stabbed with 'hundreds of tiny knives.'
Royal was diagnosed with heavy metal poisoning in April 2018. Thallium is odorless and tasteless, and can be fatal in humans.
The soft metal is used internationally in electronics manufacturing and for other purposes. It once was used in rat poison in the US, but has been banned for that use since the 1970s.
Prosecutors said Yang spiked Royal's food, beverages and mouthwash with small amounts of thallium from February through April 2018.
Royal called police for the time in February when he drank from a water bottle in his room and his tongue began to burn.
He said he woke up Yang to tell him what happened and washed his mouth out, but his tongue remained sore for a few days.
Then on March 18 Royal got sick again and police were called.
Yang, a Chinese international student, attended Lehigh University in Pennsylvania where he majored in chemistry
Prosecutors said Yang told officers that the milk in the refrigerator and Royal's mouthwash had changed color. He told officers he believed someone was tampering with the belongings in their room.
Royal became sick again on the morning of March 29 when he began throwing up and shaking. He was taken to the hospital for treatment.
About a week later, graffiti that said 'n***** get out of here' was scrawled on Royal's bed and police were called. Royal is black.
Yang provided a written statement that said he left the room and locked the door. But prosecutors said police compared the graffiti with Yang's letters and saw similarities.
The motive is not known. Months before the attempted murder charge, Yang was charged with ethnic intimidation over the racial insult.
After Yang's computer was seized, he admitted to buying chemicals online but said it was intended to harm himself if his grades started to decline.
He did admit to mixing the chemicals with food and drinks in the dorm refrigerator.
Northampton County Deputy District Attorney Richard Pepper said Royal spent about two years in physical therapy because of neurological damage from the poison, reported Lehigh Valley Live.
'Two and a half years later he’s still having neurological issues with his toes,' Pepper said in court.
Yang faces between six to 20 years in state prison when he's sentenced on January 21.
He is not a US citizen, and his student visa was revoked after his arrest. The judge told Yang he will likely face deportation to China upon completing his sentence.
'He's a believer now': Ice-T pleads with fans to take COVID seriously as he shares photo of his 'no-masker' father-in-law on oxygen indefinitely
Ice-T is urging fans to take coronavirus seriously after his father-in-law contracted a serious case of the disease earlier this year.
'My father-in-law "Coco's dad" was a serious "No masker" COVID hit him,' the actor tweeted on Sunday. 'Pneumonia in both lungs... 40 days in the ICU close to death.. Now he's on Oxygen indefinitely. Ohhh he's a Believer now.. #COVIDisNotAGame.'
The 62-year-old shared a photo of his father-in-law Steve Austin in the hospital as a stark reminder of the toll of the deadly virus.
'COVID is Not A Game': Ice-T is urging fans to take coronavirus seriously after his father-in-law contracted a serious case of the disease earlier this year
The photo has been posted before, but the impact remained.
Austin has since been released from the hospital, and Ice-T has been sharing his story in order to remind fans of serious consequences of the disease.
However, he faced criticism from some who questioned why he was getting his father-in-law involved.
'If I'm willing to use a family member that I love, as an example of someone coming close to death from a virus that I assume you think is fake.. And I'm trying to warn people.. Then it must be serious to me. Brandon you've got a lotta nerve..' he tweeted at one Twitter user on Sunday.
'I'm trying to warn people': Ice-T posted the photo to warn followers about the severe consequences of the disease, yet he faced criticism from some who questioned why he was getting his father-in-law involved
Family matters: Ice-T shares five-year-old daughter Chanel with his wife Coco Austin
Ice-T has been candid about his father's battle with the disease after initially shunning face masks, which are used to slow the spread of the disease.
'I hate to say it, but Coco's dad is a Harley-Davidson-riding, no-masking type of dude. And [COVID-19] put him on his back,' he said on the The Tonight Show Starring Jimmy Fallon over the summer.
Austin was able to tough it out at home for nine days, but eventually went to the hospital after developing pneumonia in both longs.
Though he was eventually allowed to return home after a month under the care of doctors, he still has an uphill battle.
'His lungs are damaged indefinitely': Austin was able to tough it out at home for nine days, but eventually went to the hospital after developing pneumonia in both longs
'His lungs are damaged indefinitely. COVID attacks your lungs, and it can really leave your lungs ruined,' he warned.
The actor hopes to spare others pain and potential heartbreak by sharing Austin's story online.
'I put it on social media because there's still nonbelievers... One guy wrote me and said, "You seem scared." I'm like, "Yeah, I'm scared of your contaminated breath, OK? Is there a problem with that?"' he said.
'I'm aware and I'm concerned and I'm cautious. You want to call that scared? Call it scared.'
Ice T and Coco have been married for 15 years and share five-year-old daughter Chanel together.
Doing his part: The actor hopes to spare others pain and potential heartbreak by sharing Austin's story online
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