Several countries, including the United Kingdom, are now offering a third dose of the COVID-19 vaccine because of reports that the vaccine has not worked well over time. But do these countries really need to carry out extensive promotion activities? So far, research has told us about how vaccines work.
A study showed that four months after the second vaccination, the Pfizer/BioNTech vaccine was less effective in preventing infection (classified as a positive PCR test), with the protection rate falling from 96% to 84%. However, the study is a preprint, which means that its results have not yet been formally reviewed by other scientists.
Similarly, real data from Israel shows that people over 60 who received the second dose of Pfizer vaccine in March 2021 are 1.6 times better protected from infection than those who received the second dose two months ago. However, when looking at other age groups, the data is not clear. This research has not been peer reviewed.
Moderna vaccine data shows that functional antibodies (antibodies that prevent viruses from entering cells) last for 6 months after most people are vaccinated. However, the performance of beta variants against this virus has gradually declined, and the study did not evaluate vaccines against delta variants that are now dominant.
Another preprint studied the effectiveness of the vaccine against delta and found that the Oxford/AstraZeneca and Pfizer vaccines were less effective in preventing infection when faced with this variant. The US Centers for Disease Control and Prevention also reported similar findings.
Although all these studies may sound shocking, most have not yet been formally reviewed, so their results need to be treated with caution. They also measure different things. Some people look at the number of positive PCR tests, rather than symptoms or diseases. Others consider antibody levels or responses to different variants. Indeed, when evaluating performance, we need to consider what is the most important goal of vaccination.
The vaccine still protects
The ideal vaccine can completely prevent infection, thereby preventing people from infecting and spreading the virus. However, in the early stages of the pandemic, there have been reports of people re-infecting COVID-19 and weakening of antibodies-high levels of antibodies are considered important to prevent the infection from starting. Therefore, it is suspected that it is impossible to make a vaccine that completely prevents infection.
In fact, antibodies are only an indicator of an effective immune response. We also need virus-killing T lymphocytes and immune memory, so that we can quickly produce a large number of these killer T cells and antibody-producing B cells. The news here is much more positive. Studies have shown that killer T cells and immune memory are maintained well.
This may mean that some people may not have enough antibodies to completely prevent the infection, but can still fight the infection and stop its spread. If this is the case, you would expect the vaccine to reduce the impact or severity of the disease. This is where we see the good news.
Reports in the United Kingdom and the United States show that the number of people who need to be hospitalized or have severe symptoms due to delta variants has decreased. For example, in the United States, fully vaccinated people are five times less likely to be infected with COVID-19, and are ten times less likely to be hospitalized or die from COVID-19.
Similarly, the Israeli study mentioned above shows that four months after vaccination, among 40-59 year-olds, the vaccine is 98% effective in preventing people from being hospitalized due to COVID-19. Six months later, the protection rate is still high at 94%.
However, for people over 60 years of age, the data shows that their performance declines even more, with lower protection from hospitalization after four months (91%) and six months (86%). This difference may be due to the inability of the elderly to produce a good immune response after vaccination and the challenge of delta variants.
However, it is obvious that these vaccines are very effective in preventing serious diseases compared to people who have not been vaccinated. This is indeed the most important goal of vaccination-to prevent people from developing dangerous diseases and death.
Turn on booster
Although the protection against serious diseases is still high after several months of vaccination, many governments have chosen to initiate vaccine enhancement programs. Is the third dose of the vaccine launched by the UK and other governments sufficient to provide long-term or even higher protective immunity for the most vulnerable people? The fact is, we don’t know yet.
We should remember that vaccination is just a way for us to protect ourselves from infection. If we cannot get enough protection, other measures may be needed, such as wearing masks and ventilation. In fact, in addition to boosters, the British government also outlined plans to reintroduce working from home and wearing masks in winter when the virus is out of control.
Another question we must ask ourselves is whether we should really seek to help other disadvantaged groups around the world. It is estimated that the richest countries already have enough vaccines, even with boosters and vaccinations for children.
The most important goal of vaccination is to prevent serious diseases and deaths, but many countries do not even receive the first dose of vaccine for 2% of the population, which makes the virus thrive at a huge cost of life. Really, can we look at it from another angle?