The coronavirus vaccine rollout is well underway for many countries around the world. After an applauded record development of several coronavirus vaccinations, developers are still monitoring vaccination data as they are distributed worldwide. This is a variety of reasons – to monitor safety and side effects, immunity response, understand the vaccine’s impact on groups of people and so forth. As the vaccine is rolled out to larger groups of people, developers will continue to evaluate update their efficacy claims simply due to the greater amount of data available.
Efficacy refers to the percentage reduction of disease in a vaccinated group of people compared to an unvaccinated group. Each vaccine had to go through several stages of development before they were approved as safe for wider use and rollout, one of the final trials are usually on thousands of volunteers, which gives a preliminary efficacy value. However, as the vaccine is given to millions, this percentage may change. Many vaccinations, including the Pfizer-BioNTech shot were approved in late 2020, and as we move through 2021, developers are releasing new efficacy details.
As the vaccination was rolled out quickly due to the ongoing coronavirus crisis, scientists and developers do not yet have a conclusive understanding of how long immunity against COVID-19 lasts with the vaccination, nor whether those who are vaccinated can still be carriers.
In the case of the Pfizer-BioTech vaccination, a trial has found that its vaccination protects against systematic COVID for up to six months. The Guardian wrote: ‘In a statement released on Thursday, the companies reported efficacy of 91.3% against any symptoms of the disease in participants assessed up to six months after their second shot.
The level of protection is only marginally lower than the 95% achieved soon after vaccination. The findings are the first to demonstrate that the vaccine remains effective for many months, an outcome that doctors and scientists had desperately hoped for because it suggests that people being vaccinated now should be protected at least until the autumn when boosters may be ready.’
The Pfizer BioNTech vaccination’s effectiveness varies between age groups. According to The Observer, the company has been trialing its effectiveness on younger age groups, ‘Pfizer and BioNTech said new phase 3 trial data has shown that their mRNA-based COVID-19 vaccine BNT162b2 is 100 percent effective and well-tolerated in youths ages 12 to 15.’ The vaccines overall effectiveness is apparently 94% for those 65 and older and 95% for those aged 16 and older.
The Oxford AstraZeneca vaccination was completed late last year and has already been approved and rolled out across the UK and Europe. Its original levels of efficacy were lower than Pfizer, but its levels were still beneficial, with the added bonus that this vaccination could be stored more easily than the RNA Pfizer-BioNTech version.
However, it has hit a few road bumps during rollout. This vaccine has not yet been approved in the USA, and has, until recently been undergoing trials. A press release released on the 22nd of March claimed that preliminary analysis found the vaccine to be 79% effective, in trial of over 32,000 people in the United States, Chile and Peru.
However, this claim was questioned, the US National Institute of Allergy and Infectious Disease (NIAID) were concerned that this was outdated information. Nature reported that now, ‘a key phase III clinical trial found the vaccine to be 76% effective at preventing COVID-19, the company announced on 25 March, two days after it was accused of misrepresenting interim results, which reported a slightly higher efficacy of 79%. Scientists hope the kerfuffle will not cause lasting damage to the vaccine’s reputation, which could be bolstered by scrutiny — and likely approval — by US drug regulators.’ Adding that ‘the difference between 76% and 79% efficacy is “tiny, and to be expected with the number of cases analyzed”, said Peter English, a retired consultant in communicable-disease control, in a statement to the UK Science Media Centre.’
On the US vaccine trial, the BBC reported: “the Anglo-Swedish firm has now adjusted the efficacy rate of its vaccine from 79% to 76%. Further data from the US trial showed efficacy among the over 65s rose from 80% to 85%. AstraZeneca said it now looked forward to getting US regulatory approval.
The company said the trial results confirm the vaccine “is highly effective in adults” and it remains 100% effective at preventing severe cases of the disease.” The Astra Zeneca website also added, in February, that trial ‘analysis also showed the potential for the vaccine to reduce asymptomatic transmission of the virus, based on weekly swabs obtained from volunteers in the UK trial.’