The Johnson & Johnson vaccine is 66% effective in preventing COVID-19, which seems to be a very sharp drop compared to the figures presented by Pfizer and Moderna (95 and 94.5% effective, respectively). How much should we understand in this difference, and is there a certain limit that a vaccine must reach before we can find it effective? Although the Johnson & Johnson single-dose vaccine has not yet been approved – the company is currently waiting for emergency authorization from the FDA – we can now allay some of those anxieties based on what experts know so far.
Is the Johnson & Johnson vaccine effective enough?
The Johnson & Johnson vaccine is considered effective because of how well it prevents severe cases of COVID-19, said Stanford infectious disease physician Aruna Subramanian, MD. Research has shown that Johnson & Johnson is 85% effective in this category, well above the 70% limit that Dr. Subramanian said is normally needed to be considered a high-quality vaccine. The Johnson & Johnson vaccine was also 100 percent effective in preventing hospitalization and death from COVID-19, according to clinical tests.
It is when you expand the data to include mild and moderate cases of COVID-19 that the effectiveness numbers decrease. This is normal, Dr. Subramanian told POPSUGAR, because based on the evidence we have now, we don’t know if any of the vaccines really stop you from being infected; they just stop you from developing serious symptoms after infection. Essentially, you can still breathe in the viral particles, explained Dr. Subramanian, and they will still “replicate to some degree” in your body. But with an extra boost from the vaccine, his immune system “keeps him under control so that his symptoms are only mild,” she said. “You may not have that much virus and it will get rid of it before your symptoms get worse.”
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As a side observation, having fewer viruses (i.e. fewer SARS-VOC-2 particles) in your body also helps to reduce the transmission of the virus, making it less likely that you will pass it on to someone else. A recent study confirmed that at least one COVID-19 vaccine, the AstraZeneca / Oxford option, reduces the body’s viral load in this way.
So, back to the original question: yes, the Johnson & Johnson vaccine is considered effective. Preventing serious illnesses is what matters most, and this is where the vaccine stands out.
Is the Johnson & Johnson vaccine less effective than Pfizer and Moderna?
Dr. Subramanian cautioned against directly comparing vaccine efficacy rates. One reason is that the Johnson & Johnson and AstraZeneca vaccines were tested in areas with new SARS-COV-2 mutations; both performed tests in South Africa, where strain B.1.351 emerged, and AstraZeneca additionally tested in the United Kingdom, where variant B.1.1.7 was found. These new strains interact differently with the vaccine and there is evidence that, although they are still effective, vaccines may have a harder time fighting them.
In comparison, Pfizer ran tests in South Africa, but completed data collection on October 9, when the CDC says the South African variant was just beginning to appear in tests. (The Johnson & Johnson test lasted until January.) Moderna conducted clinical tests in the United States. Since the publication of the results of clinical trials, Moderna and Pfizer have noted that their vaccines are in fact less effective against the South African strain, although they still provide protection.
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If this strain were present during the initial tests, then it is possible that the original efficacy rates of Pfizer and Moderna would also have suffered the same damage as those of Johnson & Johnson. This is not to panic about the new strains, which vaccines still protect. It is just another reason for not directly comparing the effectiveness between vaccines, because differences in factors such as the location of the clinical trial can have an impact on these numbers.
In summary, Dr. Subramanian said, “Everyone should be sure that all of these vaccines being approved are highly effective in preventing hospitalization, death and even serious illness.” And, she added, “people shouldn’t be too concerned about the vaccine they are getting.” If you are eligible to receive a vaccine, follow her advice: “go ahead and take it, because all vaccines will bring us closer to collective immunity”. Until then, and even after you get the vaccine, here’s another reminder to keep following the CDC guidelines for keeping yourself and others safe: social detachment, washing your hands often and wearing a mask (or two) .
POPSUGAR aims to provide the most accurate and up-to-date information on the coronavirus, but the details and recommendations on this pandemic may have changed since publication. For the latest information on COVID-19, check the resources of WHO, CDC and local public health departments.