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CVS registered pharmacist Ken Ramey prepares to provide a Covid-19 vaccine in ~ the island of Vero coast assisted and also independent an elderly living ar in Vero Beach, Fla.Wilfredo Lee/AP
This story was last to update on Oct. 26.

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Scientific teams around the human being have arisen successful Covid-19 vaccines in incredibly short order. In a feat that even a pair of years ago would have actually seemed totally out that reach, vaccines come protect versus the new disease were being used before the an initial anniversary that the disclosure that a new threat existed. This is truly extraordinary.

In the joined States, three vaccines room available. 2 — those native Moderna and also Johnson & Johnson — have actually emergency usage authorizations, i m sorry are environment-friendly lights from the Food and also Drug administration to it is in put right into use, also though they have not however been completely licensed. In august 2021, the FDA gave full approval to the vaccine emerged by the cooperation of Pfizer and German manufacturer BioNTech for civilization 16 and also older. This vaccine is supplied in younger teens under an EUA and is meant to be accessible for youngsters five and older through the first week of November.

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The Pfizer shot very first received emergency authorization in mid-December 2020, followed carefully by the one arisen by Moderna with help from the nationwide Institute of Allergy and Infectious Diseases.

In so late February came a third. Janssen Pharmaceuticals, the vaccine department of Johnson & Johnson, secured one emergency usage authorization for its one-dose vaccine. The vaccine was seen as a potential game-changer. The doesn’t need the fussy cold-chain necessary to keep the Pfizer and also Moderna vaccines native spoiling. That is cheaper, both ~ above a per-dose basis and because just one dose is needed. Plus that was thought a one-and-done option could entice some human being who couldn’t conveniently get two doses to role up their sleeves.

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But because the J&J vaccine’s come on the step there have actually been a variety of challenges. A manufacturing snafu in the hands of a contract production agency contaminated 15 million doses, which had actually to it is in destroyed. And in mid-April, the FDA and CDC recommended claims pause use of the vaccine as they investigate even if it is the vaccine cause a rare but serious side effect — the breakthrough of diffuse blood clots, even though the few individuals who arisen the condition had low platelet levels.

What follows is a head-to-head comparison of the vaccines arisen by Pfizer and also BioNTech, by Moderna, and by J&J. This article will be updated as breakthroughs occur.

Vaccine types

The Pfizer and Moderna vaccines room made using messenger RNA, or mRNA, a modern technology that it is provided a little bit of genetic code to cells — in effect, a recipe to do the surface protein (known together spike) top top the SARS-2 virus. The proteins made through the mRNA instructions activate the immune system, teaching it to view the spike protein together foreign and develop antibodies and other immunity weapons v which to fight it.

The J&J vaccine offers a different strategy to instruct person cells to make the SARS-2 spike protein, which climate triggers an immune response. It is what’s recognized as a viral vectored vaccine. A unauthorized adenovirus — from a huge family of viruses, some of which reason common colds — has been engineered to bring the hereditary code for the SARS-2 spike protein. Once the adenovirus beginning cells, they use that code to do spike proteins. J&J work this same technique to do an Ebola vaccine that has been authorized for usage by the European medicines Agency.


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Target population

The Pfizer vaccine has actually been authorized for usage for human being aged 16 and older, though its EUA additionally extends to youths eras 12 come 15. By part time in the very first week of November, the FDA and the Centers for an illness Control and also Prevention are expected to increase the age group extended by the EUA come include children aged 5 come 11.

Moderna’s vaccine has been clearing for usage in civilization 18 and older, though the company has submitted an application to have the vaccine’s emergency authorization expanded to incorporate youths down to the period of 12. The FDA’s decision ~ above that application is tho pending. And on Oct. 25, Moderna announced topline results of a phase 2/3 efficacy trial that had performed in kids 6 to 11. (Note the difference between the ages of the Pfizer and also Moderna pediatric vaccines.) that will use for a further extension of that is EUA and also is testing its vaccine in younger children.

At this point J&J’s vaccine is only authorized for world 18 and also older. It has actually recently began a step 3 efficacy attempt in youths aged 12 to 17, however is an extensive behind that two competitors in terms of gaining into the pediatric market.

Vaccine efficacy

The Pfizer and Moderna vaccines displayed astonishing — and essentially tantamount — degrees of efficacy, at least in the early on stages ~ vaccination.

The Pfizer vaccine showed efficacy that 95% at preventing symptomatic Covid infection after 2 doses. The vaccine appeared to be an ext or less equally protective throughout age groups and racial and also ethnic groups.

The Moderna vaccine was 94.1% effective at staying clear of symptomatic Covid-19 ~ the second dose. The vaccine’s efficacy showed up to be slightly lower in people 65 and also older, however during a presentation to the Food and Drug Administration’s advisory committee in December, the agency explained the the numbers can have been influenced by the truth there were few cases in that period group in the trial. The vaccine showed up to be equally effective across different ethnic and racial groups.

But to compare the efficacy that those vaccines come the efficacy the Johnson & Johnson’s is daunting because of differences in the designs of the phase 3 clinical exam — basically the trials were testing for various outcomes. Pfizer’s and also Moderna’s trials both experiment for any symptomatic Covid infection. Pfizer started counting cases from seven days ~ receipt the the 2nd dose that vaccine, if Moderna waited until day 14 to begin counting cases.

J&J, by contrast, search to determine whether one sheep of its vaccine protected against moderate to major Covid illness — identified as a combination of a hopeful test and also at least one symptom such together shortness that breath, start from 14 or 28 days after the solitary shot. (The company built up data for both.)

Because that the difference in the trials, making straight comparisons is a little bit like to compare apples and oranges. Additionally, Pfizer and Moderna’s vaccines were tested before the appearance of troubling brand-new variants.

The J&J vaccine was still being tested once the variants were making the rounds. Lot of the data generated in the south African eight of the J&J trial affiliated people that were infected with the variant first seen in southern Africa, dubbed Beta.


The J&J one-dose vaccine was shown to it is in 66% protective against moderate to major Covid infections as whole from 28 job after injection, though there to be variability based on geographic locations. The vaccine was 72% safety in the unified States, 66% safety in southern America, and also 57% safety in southern Africa.

But the vaccine was presented to be 85% protective against severe disease, through no differences throughout the eight countries or three regions in the study, nor throughout age groups amongst trial participants. And there were no hospitalizations or deaths in the vaccine arm of the trial after ~ the 28-day duration in which immunity developed.

The vaccines all appear to have actually lost some efficacy against infection through the Delta variant, which came to be dominant in the United states in summer 2021 — though it’s not clear how much of the efficacy decrease is due to the mutations that Delta or waning immunity together the months due to the fact that initial inoculation accumulate.

It also appears that, if the vaccines are avoiding many infections, vaccinated people who have actually breakthrough infections through the Delta variant deserve to transmit the virus to rather (though they space not as transmittable as unvaccinated people). Still, even with Delta, studies show that the vaccines have maintained their protectiveness against severe an illness and death.

Number of doses/amounts that vaccine every dose

The primary series of both the Moderna and also the Pfizer vaccines is 2 shots: a priming dose, adhered to by a booster shot. The interval between Moderna sheep is 28 days; because that the Pfizer vaccine, it’s 21 days.

Each dose of Pfizer’s contains 30 micrograms that vaccine. Moderna went through a much larger dose of vaccine, 100 micrograms. It means the firm is making use of a little an ext than three times as much vaccine per human as Pfizer is. While Moderna’s initial outcomes didn’t seem to justify the much bigger dose, data suggest the protection the this firm vaccine generates is decreasing at a slower price than Pfizer’s is; part experts think the higher dose may be at the very least partially responsible.

The J&J vaccine is, as mentioned, a single-dose vaccine. The agency has also tested a two-dose regimen, v the 2 shots offered 57 job apart. The outcomes from that 30,000-person trial to be presented throughout an Oct. 15 conference of FDA’s Vaccines and also Related biological Products Advisory Committee, as component of its application for an EUA for its booster dose. (More top top this later.)

Durability the protection

Concerns around waning immunity are driving a number of countries to market their citizens booster shots, in spite of the fact that the director-general the the world Health Organization, Tedros Adhanom Ghebreyesus, referred to as for a moratorium on offering vaccine boosters until 2022 in bespeak to speed up first doses of vaccine to low-income countries.

What shows up to it is in happening is the as an ext time overcome after vaccination, protection against all Covid epidemic starts come decline. Breakthrough cases — i m sorry are mainly mild — have started come increase. The decrease has been many pronounced amongst Pfizer recipients. Data indigenous the big health mechanism Kaiser Permanente of southern California says the waning is many pronounced against the Delta variant — the main family members of SARS-CoV-2 viruses turn in the U.S. — however even versus other variants protection has declined.


All three vaccines continue to market solid protection against severe illness, though there is problem within the Biden administration that this also will undermine if boosters room not given.

A key question in ~ this point is whether the booster shots will certainly solidify defense in a method that is an ext sustained, or if these added doses mark the start of a consistent booster shooting effort.

Booster status

For the functions of this discussion, there are two sorts of boosters.

The an initial is boosters or 3rd shots for civilization who room moderately come severely immunocompromised — due to the fact that they space undergoing chemotherapy because that cancer, since they have had an body organ transplant and are on immunosuppressive therapy, or because they have progressed or untreated HIV. These to be authorized in respectable by the FDA for the Pfizer-BioNTech and Moderna vaccines, since of growing evidence the immunocompromised world might not be protected by the typical vaccine regimen.

The plan did not apply to the one-dose J&J vaccine. The is unlikely plenty of immunocompromised world would have actually opted for this vaccine.

The second form of booster is designed to peak up protection from the early stage shot, in the case of J&J, or series of shots, in the situations of Pfizer and Moderna. All three companies have received authorizations for booster shots native the FDA.

Pfizer to be the first to document with the agency, and also its booster to be authorized in late September for human being 65 and also older, world 18 to 64 with medical conditions that progressive their risk of serious Covid, and also people age 18 come 64 whose tasks or living arrangements put them at higher risk of severe Covid.

On Oct. 20, the FDA authorize EUAs because that Moderna and also J&J’s boosters — and in the process, developed a really interesting situation. (More on this in the following section.)

Unique amongst the companies, Moderna’s 3rd shot contains fifty percent as much antigen as its first two. (This is no the instance for human being who are immunocompromised. Their 3rd dose the Moderna is a complete dose.) The emergency authorization claims — and also the CDC’s vaccine advisory committee is most likely to concur — the the Moderna booster deserve to be given to the same groups of people as the Pfizer booster.


The FDA’s statement additionally presages that the boosters will quickly be made obtainable to more people. Peter Marks, director of FDA’s facility for Biologics Evaluation and also Research, has been publicly signalling the agency’s desire to lower the age for booster doses for every — through no limitations related to medical problems or employment ar — to 40 indigenous 65.

Both the Pfizer and Moderna boosters space going to be accessible to human being six months or longer after the 2nd dose in the series.

Not so with the J&J booster. The firm had wanted the booster to be offered six months or much more after the initial shot, except in rarely circumstances. But FDA’s vaccine advisers rejected that idea, express concern about the level that protection people get indigenous the single shot. Lock recommended the everyone who acquired the J&J vaccine should be vaccinated 2 months ~ the an initial dose — with a catchup duration for human being who are already further out from their an initial shot.

Mix and match boosters

It shows up getting a booster shoot is walking to be a “choose your own adventure” form of experience after the FDA stipulated that world eligible because that boosters can choose any type of of the jabs, regardless of what brand they at first received.

There is a cultivation body of evidence that an increasing with a different vaccine might induce a wider and longer-lasting immune response — though part combinations might work better than others.

In announcing the emergency authorizations because that the Moderna and also J&J boosters, the FDA declared no preference for who gets what, or in what order. Civilization who obtained J&J can acquire a 2nd shot of Moderna (the half dose) or Pfizer. World who acquired one of the mRNA vaccines can get the J&J vaccine together their booster, the agency said.

Not declared in the FDA’s announcement is the truth that this new policy will certainly make life much easier for folks transporting booster shots, especially those make the efforts to an increase people living in permanent care, homeless house or prisons. They will need to bring only one vaccine when they go to administer booster shots, fairly than trying come match human being to their original vaccination brand.

Side-effect profile

In the vernacular that vaccinology, shots that create a selection of transient side impacts in a lot of recipients are recognized as reactogenic.

All of this vaccines — in fact, many if no all the Covid-19 vaccines that have actually reported data so far — autumn into the reactogenic category. The Advisory Committee ~ above Immunization Practices, the CDC’s professional panel ~ above vaccines, advised hospitals beforehand in the rollout that they could want to stagger vaccinations amongst employees in situation some feel as well unwell to work-related the work after being vaccinated.

The most usual side effects are injection site pain, fatigue, headache, muscle pain, and joint pain. Some human being in the clinical trials have actually reported fever. Through the Pfizer and Moderna vaccines, side impacts are much more common after the 2nd dose. Younger adults, that have more robust immune systems, reported an ext side impacts than enlarge adults.

To it is in clear: this side results are a sign of an immune device kicking into gear. They perform not signal that the vaccine is unsafe. To day there room no serious, permanent side effects associated with receipt of these vaccines, which will certainly be very closely monitored as their use expands.


There have actually been reports of severe allergic reaction to the mRNA vaccines. Both the Pfizer and also Moderna vaccines appear, on rare occasions, to trigger anaphylaxis, a severe and also potentially life-threatening reaction. Human being who construct anaphylaxis should be treated with epinephrine — the medicine in EpiPens — and may should be hospitalized come ensure their airways continue to be open. The CDC says world should it is in monitored because that 15 minutes after obtaining a Covid-19 shot, and also 30 minute if they have a background of major allergies. J&J recently revealed that a single case the anaphylaxis has actually been reported in someone who got its vaccine.

It will certainly take time come come up with a firm estimate of how typically this side effect occurs. The most recent data indigenous the CDC imply that anaphylaxis wake up at a price of about 2.5 cases per one million doses provided of the Moderna vaccine, and also 4.7 instances per million doses of the Pfizer. Countless of the people who have arisen anaphylaxis have actually a history of significant allergies and also some have had previous illustration of anaphylaxis.

The mRNA vaccines bring a tiny risk the myocarditis and pericarditis, two types of heart inflammation that are most generally seen quickly after people receive their 2nd shots, wellness officials have actually said. Males under 40 seem to be at greatest risk, an especially those age 12 come 17. Most cases reported have actually been mild and also resolved.

The J&J additionally appears to have actually a significant — thought various — problem. A small variety of individuals who received the vaccine have actually gone ~ above to develop thrombotic events in the week or two after vaccination; one has actually died. The thrombotic events include diffuse clots and also low platelet levels, one unusual mix that deserve to be dangerous if treated improperly. The normal treatment for coagulation — a blood thinner dubbed heparin — would make the problem worse, the FDA said, warning physicians to ask because that a Covid-19 vaccination history if they watch patients through that configuration of symptoms.

Safety for those who room pregnant, lactating, or planning a pregnancy

Early top top in the Covid vaccine rollout, there were no data on i beg your pardon to identify if the vaccines were safe for civilization who room pregnant or lactating. Yet after numerous studies, professionals have concluded the vaccines room safe during pregnancy and lactationand furthermore, lock are vital for these two groups to receive. This examine in the new England newspaper of Medicine, for instance, looked at the safety and security of Pfizer and Moderna vaccines in pregnant and lactating people.

The CDC and the American college of Obstetricians and Gynecologists advise that people who are pregnant or lactating should acquire vaccinated, since of the risk Covid infection poses to them.

There room a the majority of rumors do the rounds that gaining vaccinated versus Covid will certainly negatively impact a person’s capability to conceive a child. ESPN soccer reporter Allison Williams freshly announced she was quitting the network — which has actually a vaccine mandate — since she desires to have an additional child.

There is no evidence that gaining vaccinated against Covid endangers fertility. In fact, a study published last month contrasted pregnancy rates amongst patients experience in vitro fertilization, spring to view if there were differences amongst people who had actually been vaccinated, who had Covid antitoxin from infection, or had neither. “The existing study fail to recognize the distinction in the implantation or pregnancy rates between women with documented seropositivity to the spike protein and women there is no seropositivity,” the writer reported.

Storage requirements

The mRNA vaccines require an intricate cold chain, the term used to define the conditions under i m sorry vaccines need to be stored during distribution and also when they are in the doctors’ offices, pharmacies, or public health clinics where they’ll be administered.

The J&J shot does not, which means this vaccine deserve to be given conveniently anywhere — in doctors’ offices, pharmacies, mass inoculation sites, public health clinics — once supplies room adequate. It have the right to be stored for at least three months at the temperature that a continuous refrigerator.

Of the mRNA vaccines, Pfizer’s was originally the more challenging to use. It had to be shipped and also stored in ultra-cold freezers — ones that might keep the vials in ~ -94 degrees Fahrenheit. But recently, the FDA announced the the vaccine have the right to be shipped and also stored — for one month just — at temperatures of common pharmacy freezers, between -13 and 5 degrees Fahrenheit. That must make the last stage of the vaccine’s journey from production plant to syringe prepared to plunge into an arm rather easier.


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And Pfizer’s pediatric vaccine will be simpler still to administer, which might make it much more likely pediatricians will certainly become affiliated in the vaccine rollout. The 10-dose pediatric vaccine vial can be save for approximately 10 weeks at refrigerator temperatures. The limit of trust in between pediatricians and also parents will certainly be key in getting human being who are uncertain about whether they want to vaccinate their kids to agree to execute so.

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Moderna’s vaccine need to be transport at -4 degrees Fahrenheit, which is within the selection of a constant refrigerator freezer. The Moderna product is steady at fridge temperature for 30 days and at room temperature because that 12 hours. J&J’s vaccine deserve to be stored in ~ room temperature — no to exceed 77 degrees Fahrenheit — for 12 hours when the vial hasn’t yet been punctured. After the first dose is withdrawn, the vial deserve to be save in a fridge for six hours or at room temperature for two hours.

Andrew Joseph added reporting. 

An earlier version the this story mischaracterized the way in which famous vectored vaccines work and incorrectly stated that the solitary dose J&J vaccine contains an ext antigen 보다 the doses in its two-dose regimen.