Two newly published studies show that the fourth dose of covid-19 vaccine can significantly improve a person's immunity and reduce the risk of infection compared with the third dose of covid-19 vaccine. Most fourth dose programs around the world are currently limited to very elderly and vulnerable populations However, experts disagree on whether additional reinforcing needles should be provided to more age groups at present
Since the initial two dose covid-19 vaccine program was launched at the end of 2020, the question has been: when is it necessary to take another dose? With the progress in 2021 and the emergence of new sars-cov-2 variants, it is clear that three doses of vaccine is the best protection against serious diseases. But now, by 2022, many people want to know when they need a fourth dose.
A new study published in the Lancet Infectious Diseases provides one of the most powerful insights into the immune response to the fourth dose of covid-19 vaccine. The UK study closely measured various immune biomarkers in elderly subjects who received a fourth dose about seven months after the third dose.
The results showed that the fourth dose of vaccine significantly improved the antibody and T cell response, reaching a level similar to that after the third dose of vaccine. In some cases, these immune biomarkers were stronger after the fourth dose than after the third dose.
Interestingly, the study reported that the effectiveness of the fourth dose was related to the degree of attenuation of the third dose in any particular individual. Those who had sustained humoral and cellular immune responses in the third dose did not show strong benefits from the fourth dose.
The researchers wrote in the Research Report: "This finding was replicated in participants with a history of sars-cov-2 infection, indicating that there may be an upper limit or maximum anti spike protein IgG titer and T-cell response, and if the baseline response is high, the fourth dose may not improve humoral and cellular response. These individual data are important for policymakers because for those who have obtained a high level of immune response from recent infection or vaccination, the fourth dose is important The benefits of four doses may be less. "
These results were supplemented by another recently published study comparing the covid infection rates of the third and fourth doses of vaccine in a large number of elderly subjects. The study surveyed about 1.2 million people over the age of 60 in Israel. Half of the subjects received three doses of covid vaccine and the other half received four doses.
The study found that subjects who received the fourth dose of vaccine had a half lower infection rate than those who received the third dose of vaccine. This protection against infection peaked four weeks after the fourth dose. By eight weeks, the study found no difference in infection rates when comparing three and four dose cohorts.
However, in the four dose cohort, protection against severe diseases was significantly tripled. Moreover, this protection appears to have been maintained for at least six weeks, suggesting that the fourth dose may be important for the elderly and vulnerable populations.
Many parts of the world have started a fourth dose vaccine program, but there is no consensus on which people should receive additional booster shots. For example, the United Kingdom provides a fourth dose of vaccine to people over the age of 75, while the United States sets its standard at the age of 50. Most countries provide a fourth dose of vaccine for people with severe immunosuppressive diseases, but do not include other vulnerable groups, such as people with chronic diseases or cancer.
A major challenge for regulators around the world is how to widely distribute the fourth dose now. Some researchers, such as Danny Altmann, an immunologist at Imperial College London, believe that these new findings confirm the value of widely promoting a fourth dose at all ages.
Finn told the guardian: "I think it's doubtful whether young, healthy people will be offered another covid vaccine after the third dose - at least in terms of our current vaccines and variants. By (further) immunizing healthy young people with these vaccines, you won't get any very useful results because they rarely get sick - the vaccine can be prevented."
Another issue in the fourth dose debate is the possibility of strengthening the injection of Omicron specific vaccine. Both Moderna and Pfizer are in the late stages of developing more targeted booster vaccines, but it is unclear when these new vaccines will arrive.
Both companies are studying ba for Omicron Reinforcing needle of subtype 1. The problem is that the recently emerging Omicron subtypes (BA. 2.12.1, BA. 4 and ba. 5) are suspected to be able to escape ba 1 immunity from infection.
Therefore, although Moderna estimates that it can prepare new reinforcing needles from September, this time frame is based on BA 1 is the correct antigen target hypothesis. Some virus evolution experts recently warned that the virus is evolving rapidly and the production of variant specific vaccine will be too slow.
French vaccine researchers Paul loubet and idile launey suggested that people should not wait for these new variant specific vaccine formulations to appear. They believe that it is now necessary to vaccinate vulnerable people with booster shots to help reduce the incidence of serious diseases in the coming months.
In a review in the lancet, the two researchers wrote: "heterologous booster needles using next-generation vaccines, such as multivalent vaccines (vaccines that protect different variants at the same time), universal coronavirus vaccines, vaccines that cause stronger T-cell responses, or mucosal vaccines (intranasal or oral) , is one of the future options for covid-19 vaccination. However, while waiting for these next-generation vaccines, strengthening immunization is crucial to restoring the effectiveness of the vaccine's serious consequences for clinically vulnerable populations. "
The UK's fourth dose of vaccine research was published in lancet - infectious diseases 00271-7 / fulltext), Israel's fourth dose vaccine research was published in New England Journal of medicine 》Come on.