Skip to Main Content
Contribute Try STAT+ Today

Scientists at the Food and Drug Administration endorsed the Covid-19 vaccine developed by Moderna as safe and efficacious on Tuesday, one day after the first doses of a competing vaccine from Pfizer and BioNTech were delivered across the United States.

The FDA reviewers said that the two-dose vaccine “was highly effective” in preventing symptomatic Covid-19 from occurring “at least 14 days after the receipt of the second dose.”

Vaccine-related side effects, such as aches and pains, appeared more severe than with the Pfizer/BioNTech vaccine, though such comparisons should be made with caution and are in no way expected to slow the clearance of the vaccine or present major concerns. There was also preliminary evidence that the vaccine has some efficacy after one dose, and that it prevents asymptomatic Covid-19 cases — those that occur without a person ever feeling ill.

advertisement

Moderna disclosed Nov. 30 that its vaccine decreased symptomatic Covid-19 infections by 94% in clinical trials, while also preventing more severe forms of the disease. But the release of FDA documents provides the most complete look yet at what is likely to be the second Covid-19 vaccine cleared for emergency use against the disease.

The documents were released ahead of a Thursday meeting of outside experts convened by the FDA, the final step before regulators are all but sure to issue an emergency use authorization for the Moderna vaccine. Moderna has asked that its vaccine be authorized for people over 18; the Pfizer/BioNTech vaccine was authorized for people over 16.

advertisement

At Thursday’s meeting of the Vaccines and Related Biological Products Advisory Committee, the agency will seek the opinions of outside experts who will vote on whether the benefits of the Covid-19 vaccine, mRNA-1273, outweigh its risks. Though the FDA does not have to follow the recommendations of these panels, it usually does.

Moderna previously disclosed clinical trial data showing that 185 cases of Covid-19 occurred in those who received a placebo injection, which was given to half the volunteers in its 30,000-person study. Just 11 cases occurred in those volunteers who received the vaccine.

There were 30 cases of severe Covid-19 in the placebo group of the study, with none in the vaccine group. One volunteer in the placebo group died of Covid-19, compared to none in the vaccine group.

About 10% of volunteers in Moderna’s trial identified as Black, while 20% were Hispanic or Latinx, 5% were Asian, and just under 1% were Native American. In September, Moderna slowed down the enrollment of its trial in an effort to include more participants from underrepresented racial and ethnic groups. 

Like the Pfizer/BioNTech vaccine, mRNA-1273 utilizes a new technology that uses a synthetic version of messenger RNA or mRNA, a key messenger chemical that living things use as part of the process that turn DNA code into the proteins that make up all cells. 

That both of these vaccines use this new technology is a vindication for Moderna, which raised billions of dollars from investors based on the potential for mRNA technology but until now had not delivered a product.

But the Moderna and Pfizer/BioNTech vaccines are not identical. One difference: Moderna’s vaccine tended to cause more vaccine reactions in clinical trials, such as fevers, aches, and chills, than the Pfizer/BioNTech vaccine. 

Severe reactions — which would lead patients to be briefly impaired, but not hospitalized, appear more common with the Moderna vaccine than with the Pfizer/BioNTech one, although comparisons from different trials can be misleading. In the Moderna study, 15.8% of patients had a severe, or grade 3, reaction. Rates of fever and severe fever were similar between studies. In the Moderna study, 65.3% had fatigue, 9.7% of it severe; muscle pain occurred in 58% of patients, 9% severe; joint pain 42.8%, with 5.2% severe.

In the Pfizer/BioNTech study, 59% of volunteers reported fatigue, 4.6% of them severe. Muscle pain occurred in 37.3% of those receiving the Pfizer vaccine. Joint pain occurred in 21.9% of recipients.

However, there were also different side effects between the placebo groups in the two studies. Rates of fatigue were similar, at 23%, in both placebo groups; muscle pain occurred in 12.4% of placebo patients for Moderna and 8% for Pfizer/BioNTech, and joint pain in 10.8% for Moderna and 5.2% in the Pfizer/BioNTech.

These types of reactions are generally expected as a result of the immune response spurred by a vaccine, and are not likely to present an issue to regulators or to doctors administering the vaccine.

FDA reviewers also noted an imbalance in cases of Bell’s palsy, a temporary weakness in muscles in the face, which also occurred with the Pfizer vaccine. There will be monitoring for this side effect. As with the Pfizer/BioNTech vaccine, FDA reviewers noted data that could be an indication of mild allergic reactions. After the Pfizer/BioNTech vaccine started being given in the United Kingdom, there were two reports of severe allergic reactions that had not been seen in clinical trials, leading to increased concern about those side effects.

Moderna said that it has conducted a developmental and reproductive toxicity study, used to assess giving a vaccine in pregnant women, with no adverse effects. Pfizer/BioNTech are still conducting such a study.

One encouraging finding with the Pfizer/BioNTech vaccine was that it appeared possible a single dose of the vaccine was effective in preventing Covid-19. Moderna is presenting a different analysis of the same question, looking at Covid-19 tests that were administered to patients at their first and second doses of the vaccine.

At the second injection, there were 14 cases that tested positive for Covid-19 in the vaccine group, compared to 38 in the placebo group. None of these patients had symptoms. Although the numbers are small (there were more than 14,000 patients in each group) they may indicate that one dose of the vaccine is somewhat effective in preventing the disease, and that the vaccine prevents asymptomatic cases.

  • This article is lacking so much information and is just filled with fluff like every other media source out there. Its extremely unfortunate the journalists we have to convey the information we need as a society. After initially read th quote, “But the Moderna and Pfizer/BioNTech vaccines are not identical.”, one is lead to believe they are about to find out a legitimate difference between the vaccines which would inform us on how to chose should we get an option which vaccine we would prefer over the other. That lead-on is sadly followed by this deflated sentence, “One difference: Moderna’s vaccine tended to cause more vaccine reactions in clinical trials, such as fevers, aches, and chills, than the Pfizer/BioNTech vaccine” is not a response that the vaccines are not identical, but is a mere statement that the reactions of both vaccines are different; An obvious conclusion of every vaccine ever made. This is not the only pitiful article out there by any stretch of the imagination. It merely compounds the fact that our news outlets do minimal research and digging before churning out articles meant to be “informative”. It is not adding any value or knowledge to readers whatsoever.

  • what if I have already problem with joint sometime severe pain and I’m taking GABAENTIN 400mg three times daily

  • I don’t follow the thread on asymptomatic ? Did moderna test all participants or just symptomatic participants ? If asymptomatic not tested and 45% are asymptomatic then effective rate must be much lower?

  • I have a history of severe allergic reactions to antibiotic including anaphylaxis liver failure and nearly needing blood transfusion from 3 different antibiotics this concerns me so since 2 of my reactions nearly killed me so makes me very concerned of the vaccine which i will probably not take

    • Dr Faucci stament if you have had a previous reaction to a injection do not take because your reaction could have a worse reaction.

  • Author, that you for putting more data into this article especially the side effects and the asymptomatic.

  • “There was also preliminary evidence that the vaccine has some efficacy after one dose, and that it prevents asymptomatic Covid-19 cases — those that occur without a person ever feeling ill.”

    The above statement is one of the biggest positive for Moderna. It is important not only to prevent symptomatic but also asymptomatic as asymptomatic shed virus longer than symptomatic.

    https://www.medpagetoday.com/infectiousdisease/covid19/87168

    “Moderna disclosed Nov. 30 that its vaccine decreased symptomatic Covid-19 infections by 94%”. Does this mean that if you included the decreased in asymptomatic, the success rate is higher?

    Since the efficacy is 94%, people should not assume just people they have the vaccine they will fall into the 94%. People should stay being careful assuming that maybe they can fall into the 6%. The worst case is someone who got vaccinated, became asymptomatic and then lower their guard since they think they are protected and then start infecting other people.

    Author, is there is link for the documents that Moderna does prevent asymptomatic? If nobody became asymptomatic during the clinical trials, then this is a big win for Moderna.

  • The biggest variable is dosing, as empirically discovered with the Moderna vaccine. This is how many great scientific developments have started : by a happenstance event with intelligent “eureka” analysis. It appears worthwhile to follow up with different / lower dosages towards the desired immunity effect.

  • There is much subjectivity in “grey area” side effects like joint/muscle pain, fatigue, chills, etc. Only fever is objectively measurable, but is not differentiated in this article. It seems that each company just had different symptom criteria, language and results rendition. With such young vaccines, on a new vaccine platform, so quickly developed: any issues or additional benefits will just show as people get vaccinated. We are all guinea pigs, and for many this is pallatable as safety requirements seem to have been met.

  • I’m trying to understand whether the Moderna vaccine would also prevent asymptomatic spread (for the Pfizer vaccine, the answer is “we don’t know”). I’m a bit confused by the last paragraph. Wouldn’t the 14 asymptomatic cases imply that the answer is “no”, asymptomatic cases are not prevented? Or is the comparison with the 38 in the placebo group, i.e., 38-14=24 fewer asymptomatic cases?

    • Yes given the trial is a randomised placebo control trial with 50% receiving the vaccine the statistic is (14/38)-1= 63% efficacious in reducing asymptomatic infection relative to the baseline established by the placebo.

      Obviously this was not an endpoint of the study (to my knowledge) and the study was not powered to show statistical significance.

    • I believe that was data collected at the time of providing the second injection, so already by that point, the vaccine seems to be preventing asymptomatic cases. Hopefully it also means that after the second injection it is preventing both symptomatic and asymptomatic cases.

    • @OC, @Katie — thanks for your reply!

      So, it would appear that the Moderna/NIH vaccine will contribute to developing herd immunity. Hopefully the Pfizer/BioNTech will too, and simply there are no data about it yet.

    • Mike, thank you. I miss that 14 becomes cases.

      “At the second injection, there were 14 cases that tested positive for Covid-19 in the vaccine group, compared to 38 in the placebo group. None of these patients had symptoms.”

      It seems that there is still asymptomatic cases after the second injections. This is the disturbing factor, people get vaccinated, becomes asymptomatic yet they assume since they had the vaccine, that they are immune. I think even if people who had been vaccinated, they should still do covid test if they think they are at risk or if their profession demands it periodically.

      The last thing we want is this newly vaccinated asymptomatic people spreading this to the people who did not get vaccinated.

    • @livi How I’m reading it is that when participants came in for their 2nd injection, they also received a covid test and that’s when they found the 14 asymptomatic cases. Therefore, the 2nd shot hadn’t had time to work yet– I’m still seeing this as super promising news!

  • Facts:

    Much worse and more frequent side effects.

    No mention to Moderna being only 86% effective in the over 65 group.

    Moncef Slaoui (head of Warp Speed) ex board member of Moderna…

    • FACT: Reporting of side effects is subjective. Double the rate of side effects in moderna PLACEBO control arm STRONGLY suggests they used language and a course of questioning MUCH more likely to ellicit a positive response to the questions re side effects.

      Or are you suggesting the saline they used was 2x as likely to cause a side effect?

      FACT: 100% reduction in severe cases of COVID-19. I.e. the thing that kills people.

      FACT: You don’t have to get it if you don’t want to. Sit there unprotected if you feel so strongly about it.

    • I just got my shingles vaccine and after both shots I felt like I’d been hit by a truck for a day — definitely worth the inconvenience. Even feeling like that for a whole week would be a more than acceptable price for me to pay, to be protected from death or permanent organ damage due to Covid-19, and not to worry about infecting others.

    • All I am saying is that there is a much better vaccine out there (Pfizer/Biontech) and US should do everything to help them ramp up production.

      I would definitely agree with the Moderna vaccine if it was the only choice.

      As I look at the Moderna submission I see many inconsistencies that make me think that approving would greatly lower the public’s confidence in vaccines.

      I agree that “the double the rate of side effects in moderna PLACEBO control arm STRONGLY suggests they used language and a course of questioning MUCH more likely to elicit a positive response to the questions re side effects”. This is worrisome as it may be an attempt to make the ratios look better (anyway ratios are much worse than for the Pfizer/Biontech one). Let’s compare to saline side effects in placebo in similar studies.

      It’s great that they have 100% reduction in severe cases. But why so much more severe cases then in the Pfizer/Biontech study? “Subjectiv” criteria or protocol implementation I bet.

      Should a young person take a Moderna vaccine with strong/frequent side effects hoping for no long term nasty side effects? Or the Pfizer/Biontech one?

      Should an older person take an 86% efficacy Moderna vaccine with strong/frequent side effects hoping for no long term nasty side effects? Or the 94% efficacy Pfizer/Biontech one?

      I know what I will choose. I also know what FDA will choose.

Comments are closed.