As Johnson & Johnson’s (J&J) COVID-19 vaccine received Emergency Use Authorization from the US Food and Drug Administration (FDA) on February 27 (please refer to: As for whether or not to get vaccinated — you should know what Emergency Use Authorization is — the US currently has three COVID-19 vaccines to “choose from”. Pfizer’s and Moderna’s are both mRNA vaccines, while J&J’s are adenovirus vaccines, which are also Spike proteins encoding the Novel Coronavirus. So far, Pfizer and Moderna have both been cryogenically frozen and require two doses, but Johnson’s vaccine is poised to become the next big thing because of its easy storage (up to three months in an ordinary refrigerator) and one-shot advantage.
How protective is Johnson & Johnson’s COVID-19 vaccine?
Johnson & Johnson’s ad26.cov2.s vaccine is suitable for people over 18 years of age and its Phase III clinical trial demonstrated 66% effectiveness in preventing symptomatic COVID-19 infection after a single dose. On a numerical basis, the response rate is significantly lower than Pfizer’s and Moderna’s 95% + response rates. But the data on vaccine effectiveness is not so simple as to judge one from the other. The three vaccines had different clinical trial designs, making direct comparisons of data difficult. According to the data available so far, all three vaccines are effective in preventing hospitalizations and deaths in COVID-19 patients.
A single dose of Johnson & Johnson’s vaccine is its advantage
Vaccination has two effects: it reduces an individual’s chance of contracting the virus, and when enough people are vaccinated, it increases the immunity of the entire population (so-called herd immunity), which greatly reduces the spread of the virus and may even protect those who are not vaccinated. So in the case of a pandemic, the speed of vaccination will determine who wins in the human and novel coronavirus race. J&j seized the opportunity to obtain emergency authorization for use in a Phase iii clinical trial that began in September of last year, in which a single dose of the vaccine was studied and met the FDA’s basic requirements for a vaccine. The emergence of a j&J vaccine is set to dramatically accelerate the pace of vaccination in the United States and change the COVID-19 pandemic.
Can the mRNA vaccine also be given as a single dose?
The Pfizer and Moderna vaccine trials both looked at 95% or more effectiveness after two doses (three weeks apart for Pfizer and four weeks apart for Moderna). How do you get more people vaccinated in a shorter period of time, as the supply of vaccine is far in short supply? The UK and Denmark have extended approvals for two doses to as long as three months to ensure that more people get at least one dose in the shortest possible time. In theory, a single dose of Pfizer or Moderna might provide enough protection in people with healthy immune systems, but two doses would provide better protection in those who are older or immunocompromised (who are also at high risk of COVID-19). But the FOOD and Drug Administration (FDA) and the CENTERS for Disease Control and Prevention (CDC) are adamant that because the companies are conducting two-dose trials, current data do not support the idea of a single dose, arbitrarily changing the interval or changing the dose (halving the dose to increase the number of people vaccinated), and so on. Another concern is whether low immunity in a population following a single dose of vaccine might make the virus more vulnerable, increasing the chances of vaccine-resistant mutations.
A single dose of j&J’s vaccine may also be a disadvantage
Although the vaccine has been given a “one-shot” response, the vast majority of COVID-19 vaccines currently in clinical trials and authorized for emergency use are studying protection after two doses. Why is that? A review of more than 100 years of vaccine development shows that the vast majority of vaccines require two or more doses within a certain period of time to achieve optimal protection. After the first dose of vaccine, there is a Primary response, in which the body activates B lymphocytes to produce antibodies against an antigen, and then the number of antibodies decreases dramatically over time. A second dose of the vaccine causes B lymphocytes to mature to produce more and better antibodies, and a type of memory T cells, which can live for decades in a dormant state in the body, Until it encounters the antigen again, it quickly activates the immune system to produce a Secondary response to the infection. Thus, two or more doses of vaccine are behind the underlying characteristics of the human immune system. Of course, it doesn’t mean that one dose won’t work, but the flu vaccine we get every year is a “one in place” dose.
Does the Johnson & Johnson vaccine require an annual dose like the flu vaccine?
The annual flu vaccine, except for children, is given in one dose. One reason is that the mutation of the influenza virus is extremely rapid, and the strain type of the epidemic is different every year. The second is that the annual flu season only lasts four to five months of winter. Although flu vaccines tend to be only about 40 to 50 percent protective each year, the temporary immunity created by a single dose is enough to temporarily cope with that year’s flu season.
For novel Coronavirus, although multiple variants were frequently reported in various places, the mutation rate of SARS-COV2 virus was much lower than that of influenza virus due to the “reading mechanism” carried by RNA viruses themselves and the slower mutation of the common characteristics of coronaviruses. As we learn more about the novel Coronavirus, it remains to be seen whether future COVID-19 seasons will follow us in the same way as flu seasons. So it is too early to predict whether annual vaccination will be needed, like the flu vaccine.