As early as a few months ago, many people have completed two doses of the new crown virus vaccine, and now the reinforcement needle is coming, why supplement this needle, what role can the strengthening needle play, is the vaccination safe?
Antibodies decrease month by month
Vaccine protection is also reduced
Vaccines block the new crown virus from invading cells, mainly by stimulating B cells in the human immune system to produce antibodies, interfering with the binding of viral surface proteins to human cell membrane receptors.
After vaccination against COVID-19, antibody levels rise rapidly over a period of weeks and then gradually decrease over time. Studies have shown that at the same time, vaccine protection is reduced, and the risk of contracting the new crown virus and developing severe disease is increased.
A study published in the New England Journal of Medicine (NEJM) in early October showed that antibody levels decreased six months after receiving the BNT162b2 COVID-19 vaccine. The 4668 people who participated in the study were doctors, nurses and other workers at a large hospital who underwent antibody levels every 4 weeks after vaccination, for a total of 6 measurements. The results showed that after receiving the second dose of the vaccine, the participants' antibody levels peaked on days 4 to 30 and then gradually decreased over time[1].
After the second dose of the vaccine, IgG antibodies (antibodies that appear late and last for a long time)
Levels decreased month by month, with Log IgG below one-tenth of its peak at 6 months | References[1]
The level of neutralizing antibodies (antibodies that bind directly to the virus) also gradually decreases, and the ability to neutralize is significantly weakened | References[1]
As for whether the reduced antibody level represents a decrease in the protection of the vaccine, Nature also wrote an article on September 17 this year to discuss it. Two immunologists said in interviews that over time, the neutralizing antibodies that bind directly to the virus decline rapidly, while memory B cells can still play a role when the body is re-exposed to the virus [2].
However, some experts believe that the prevention of infection mainly relies on neutralizing antibodies, and the longer the interval between vaccination and exposure to the virus, the more likely it is to be infected and the more serious the disease. For example, elderly people vaccinated in Israel in early 2021 were twice as likely to develop severe illness during the July outbreak than those who were recently vaccinated. Similarly, Israeli reports on third doses of boosters indicate that people who have been vaccinated have a lower chance of infection and a lower chance of developing severe illness than older adults who have not received a third dose [3], and we will cover this study in more detail later.
The article also discusses other benefits than directly protecting vaccinated people from infection and progression to severe illness. For example, vaccination can reduce the prevalence of the virus in the population and reduce the probability of others being infected. If the virus is widespread, it also means that there is a greater risk of developing dangerous mutated strains. Therefore, the strengthening needle can reduce the prevalence of the virus in the human population in many ways.
For the domestic COVID-19 inactivated virus vaccine, clinical trial data from Kerriff Vaccine of Kerring Company showed that the neutralizing antibody titer rose to 49.1 after receiving the second dose of vaccine, and dropped to 6.7 after 6 months, below the seroprevalence threshold. Similarly, between the 28th day and 3 months after receiving the two doses of Sinopharm vaccine, the titer of neutralizing antibody decreased significantly by 35.8% to 70.8%.
In the face of gradually decreasing antibody levels and vaccine protection, some countries and regions have begun to introduce new measures to strengthen epidemic prevention and control.
Booster needles increase antibodies
Reduces the risk of infection and severe illness
As mentioned in the previous study in Israel, the protective effect of the BNT162b2 vaccine has decreased over time, and therefore the intensive vaccination has been introduced in Israel since 30 July 2021: if the second dose is more than five months away and the age is greater than or equal to 60 years, the third dose of the vaccine is started.
One study collected data from the following month, compared infections among more than a million participants, and published the results in the New England Journal of Medicine on Oct. 7. The study found that people who received a third dose for more than 12 days were infected with the new crown virus less than one-tenth of those who received two doses, and the severe illness rate was close to one in twenty. Compared with people 4 to 6 days after the third dose, the risk of contracting the new crown virus after 12 days of vaccination is also reduced by about four-fifths [3].
Compared with those who did not receive the booster needle, the proportion of vaccinated people with infection and severe illness decreased by | References[3]
Another study, published October 29 in Lancet, focused on the role of a third dose of BNT162b2 in reducing severe cases [4]. The study included 1.15 million people receiving the third dose and selected 720,000 unoculated people with similar characteristics as a control. The results showed that 29 of those who received the third dose were hospitalized due to COVID-19 infection, including 17 cases of severe illness, while those who received only two doses of the vaccine were hospitalized and 157 cases of severe illness, respectively. The study concluded that a third dose of COVID-19 vaccine can effectively reduce the risk of severe illness on the basis of two doses.
People who receive three doses (blue) are less likely to be admitted to the hospital for COVID-19-related reasons than people who receive two doses (red) | References[4]
Three doses are given a lower rate of severe COVID-19 than those given two doses | References[4]
Three doses are given a lower proportion of COVID-19-related deaths than those given two doses | References[4]
Data from studies on the third dose of the Kerraf vaccine were also uploaded to medRxiv in July 2021 [5]. The study included 540 participants aged 18 to 59 years, and the results showed that when the third dose was given 6 to 8 months after the second dose, the neutralizing antibody titer increased by about 20 times after 14 days.
Sinopharm vaccine-related studies also support the enhanced effect of the third dose, but no peer-reviewed articles have been published.
The safety of the third dose is similar to that of the first two doses
Finally, let's look at the safety of the reinforcing needle, the safety of the first and second doses of the new crown virus vaccine has been verified in the vaccinated population, and the third dose may be similar to the previous one.
In February 2021, a study related to the safety of the first and second doses of the Kerraf vaccine was published in The Lancet [6]. The study documented reactions in 144 adults after receiving a vaccine or placebo injection, and all groups of participants experienced adverse reactions after the injection. Among the various adverse reactions, the incidence of discomfort symptoms at the injection site and pain at the injection site in the vaccine group was significantly higher than that in the placebo group, and there was no significant difference in other adverse reactions.
The incidence of adverse reactions in the vaccine group (green and blue) and placebo group (red) was | References[6]
In the third dose vaccination study, 540 people who received the Kerraf vaccine had a total of 14 adverse reactions in the 28 days after the third dose, which was similar to the incidence of adverse reactions in the first dose, with a severity of 1 to 2 degrees, and the most common reaction was pain at the injection site. The researchers' analysis suggests that no serious adverse reactions are associated with vaccination [5].
In summary, the third dose of the new crown virus vaccine is safe and effective. Giving a third dose about 6 months after the second dose of the vaccine can increase the antibody level again, and the third dose of the vaccine can also effectively reduce the number of infections and severe cases. In addition, the specific vaccination of the booster needle depends on the local epidemic situation and the individual's risk of infection.
bibliography
[1] Levin EG, Lustig Y, Cohen C, et al. Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months [published online ahead of print, 2021 Oct 6]. N Engl J Med. 2021; NEJMoa2114583.
[2]https://www.nature.com/articles/d41586-021-02532-4#ref-CR8
[3] Bar-On YM, Goldberg Y, Mandel M, et al. Protection of BNT162b2 Vaccine Booster against Covid-19 in Israel. N Engl J Med. 2021;385(15):1393-1400.
[4] Barda N, Dagan N, Cohen C, et al. Effectiveness of a third dose of the BNT162b2 mRNA COVID-19 vaccine for preventing severe outcomes in Israel: an observational study. Lancet. 2021;0(0).
[5]https://www.medrxiv.org/content/10.1101/2021.07.23.21261026v1
[6] Zhang Y, Zeng G, Pan H, et al. Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine in healthy adults aged 18-59 years: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial. Lancet Infect Dis. 2021;21(2):181-192.
Author: Phylicia
EDIT: Transparent
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