How do the three Covid 19 vaccines compare?

The increasing Covid 19 vaccine supply

The Johnson and Johnson Covid 19 vaccine is finally available.

I have been receiving questions about how safe and effective it is compared to the Pfizer and Moderna vaccines. So here is a succinct summary that I hope will be helpful to you.

Number of Vaccine Shots Required

  • Pfizer vaccine – 2 shots – 21 days apart (although they can be up to 42 days apart if the vaccine is hard to get)
  • Moderna vaccine – 2 shots – 28 days apart
  • J&J vaccine – 1 shot only (J&J is currently testing the effect of a booster shot on antibody levels)

Efficacy of the Covid 19 vaccine shots

  • Pfizer vaccine – after the required 2 doses – prevents 95% of symptomatic Covid infections across age groups and racial and ethnic groups (tested 7 days after last dose)
  • Moderna vaccine – after the required 2 doses – is 94% effective at preventing symptomatic Covid infections (tested 14 days after last dose)
  • J&J vaccine – after the single required dose – is 85% protective against severe Covid illness. A severe Covid illness is defined by J&J as a combination of a positive test and at least one symptom such as shortness of breath. (This was tested for both 14 and 28 days after dose). It is between 66%-72% protective against moderate/severe infections (tested 28 days after dose)

Note – It is important to remember that most viral vaccines are considered acceptable if effective over 50%. For reference purposes the flu vaccine is around 60% effective.

Genetic Vaccine Components

  • Pfizer and Moderna vaccines- use mRNA single strand genetic instructions. This means the vaccine content doesn’t have to enter the nucleus of a cell to be turned into the needed viral ‘spike’ protein. The vaccine material never mixes with our own DNA. It is carried to the cell inside a nano-sized membrane sphere (not alive), and released to the protein factories in the cytoplasm
  • J & J vaccine – uses double stranded DNA genetic instructions, which are carried into the cells by an often-used-in-medical-labs adeno virus. The DNA is injected into the cell by the carrier virus and then must first enter the nucleus (amongst our own DNA). There it is turned into the single strand mRNA, and sent outside the nucleus to the protein factories in the cell.

Note – No Covid infection is possible from any of the vaccines!

Note – No adenovirus infections occur with the J & J vaccine. They have been stripped of their ability to reproduce.

Safety of the Covid 19 Vaccines

The Pfizer and Moderna vaccines mainly have mild local and body effects with the first dose. With the second dose, up to 15% of people may have more noticeable body effects, like headaches, muscle aches, fever lasting several days. This can be uncomfortable in a flu-like way, but it is a good sign that the immune system is developing well. In fact younger people are more likely to notice these effects because their immune systems are stronger than those of older people.

Allergic reactions are low because these mRNA vaccines do not contain the egg or latex allergens. See this Moderna Fact sheet for details of what they do contain.

Anaphylaxis (a severe immune response) is possible with both vaccines, but is very uncommon. It occurs in only 4 out of 1 million doses for Pfizer, and about 2 out of 1 million doses for Moderna. They usually occur within the first 15-30 minutes after a shot, which is why all receivers of the vaccine are kept under observation for 15 minutes before being allowed to leave. They occur more often in people who have severe allergies or have had anaphylactic reactions before.

The J&J vaccine may provide both local and systemic effects in the day or so following the one dose (it is a larger dose than the individual doses of the other two vaccines), but also seems very safe. So far only one recorded anaphylaxis reaction has been noted. See this J&J Fact sheet for details of what is contained in the vaccine.

Storage of Vaccines

The mRNA vaccines (Pfizer and Moderna) require careful cold storage which has been a definite limiting factor in vaccination procedures.

  • Pfizer has recently announced that its vaccines can be shipped and stored (for a 2 week period) in normal pharmacy freezers (-13 to 5 degrees F), which is a big improvement.
  • Moderna’s must be shipped and stored at -4 degrees F (within regular refrigerator freezer temperatures).
  • On the other hand, J&J’s vaccine can be stored at least 3 months at regular refrigerator temperatures, and 12 hours at room temperature. This makes it by far the easiest vaccine to distribute.

Durability of Vaccine Protection

How long our protective antibodies will last, and when/if we’ll have to get boosters is currently unknown for each of the three vaccines. All vaccine producers are working on boosters.

Vaccine Protection from Virus Transmission

Although the vaccines all protect us from severe symptoms of the Covid 19 illness, it is not known how well any of the vaccines prevent us having asymptomatic infections and transmitting the virus to others. This is why vaccinated people should keep wearing masks and social distancing until further studies give us the answers we need.

Vaccine Protection against Variants of the Covid 19 Virus

Variants of the original vaccine arise because the SARS-CoV-2 virus (Covid 19) is an RNA virus. These viruses change much more rapidly than the common DNA viruses. Every time they make a copy of their genes they make one or a few mistakes. And they copy themselves many, many times in every sick body!

These mistakes are called mutations, and sooner or later a mutation helps the virus in some way. Perhaps they can link up to the host’s cells more strongly. Perhaps they can invade the cells more quickly. Or perhaps they are better at hiding from the immune cells. With such an advantage they can reproduce more quickly than the other virus cells, and soon a ‘new variant’ appears.

The effectiveness of the 3 vaccines has not been particularly challenged by the U.K. variant but they have all noted some drop of effectiveness against the S. African variant, with the J&J vaccine dropping the lowest. However so far they all maintain good protection against severe disease.

The vaccine-producing companies are continually monitoring the type of Covid 19 found in new infections with an eye to modifying the vaccines if new mutations extend past the vaccine’s effectiveness. Moderna is already considering changes to the second dose.

Use in pregnant women

The American College of Obstetricians and Gynecologists (ACOG) and the CDC both recommend making any of the three vaccines available to pregnant and lactating women who fit within the risk category currently being vaccinated. At the same time they encourage them to talk with their health provider. Meantime Pfizer and Johnson&Johnson are currently conducting trials involving pregnant women.

Note – Neither previous animal testing, nor pregnancies occurring within vaccination trials indicate raised risks.

Use in children

At this time, the Pfizer-BioNTech vaccine is authorized for ages 16 and up, and the Moderna and Johnson & Johnson vaccines are authorized for ages 18 and up. There are no immunizations available from any of the companies at present for children under 16.

Trials have been going on since December in both Moderna and Pfizer involving adolescents ages 12- 18, and vaccines for that age group may be available sometime in the summer. Whether they will be widely available before the fall is uncertain.

Younger children – “The CDC’s Advisory Committee on Immunization Practices (ACIP) meets regularly to provide updates on a variety of vaccine-related issues, but for months now, there has been a call for the need for pediatric COVID-19 vaccine trials. Moderna has begun testing its vaccine in children ranging from 6 months of age to 12 years old. Pfizer-BioNTech also has vaccine trials that are currently being performed in adolescents. Johnson & Johnson is expected to follow suit, and trial investigators have already begun with the Oxford-AstraZeneca vaccine in children 6 years and older“. HCP Live

However it is likely that no younger children’s vaccines will be available for the Fall 2021 semester. The body weight and immune system in a child 6 months old varies enormously from that of a 5 year old, which in turn varies a lot from that of a 12 year old. All of which means that the dosage safety testing will take longer in children than it did in both adolescent and adult groups, who are much more similar to each other.

Vaccine makers usually work from the oldest children down to the youngest, so vaccines will probably be available in the 10-12 age range first.

Were any of the vaccines produced using embryonic stem cells?

See my answer in this post

The bottom line?

The three vaccines are similarly safe, and protective against severe Covid 19 disease. They also share the same currently unknown features. I will keep you updated about those features as more becomes known

So while vaccines are still in short supply I would encourage you to take the first one that becomes available to you.

Let me know if you have further questions.


Is there an ethical problem with the J&J vaccine?

A few days after the J&J vaccine was released, it became a controversial talking point when the Roman Catholic Archdiocese of New Orleans urged its parishioners to avoid this vaccine, calling it “morally compromised” because it was developed and tested using cells derived from aborted fetal tissues (NBC News, March 2)

Many Christians are now very concerned. Should they avoid this vaccine, even if it is the only one for which they can get an appointment?

Let’s talk about it, but before reacting to the Archbishop’s ethical statement we first need to be very clear about the medical science involved.

The Archbishop is talking about tissue-derived cell lines, not embryonic stem cells, as some of us have heard reported.

Cell lines begin as tissue cells grown in lab dishes which continue to produce the same cells over and over and over, as long as specific nutrients are provided. As one container fills up, some of the cells are moved into new containers where they have room to continue to grow indefinitely. The process is continually repeated.

Perhaps some of you have experienced making sour-dough bread? Maintaining the sour-dough starter is very similar to maintaining cell lines. Continuing to add the milk, flour, and sugar means that the starter keeps reproducing itself. The starter you had a week ago is the same as the one you have now – there is just more of it. And you give it away, don’t you? (Anything to avoid having it take over the fridge!) After a while all of your friends possess the same sour dough starter in their fridges.

In a roughly similar way, two particular tissue cell lines – with the unlikely names of HEK293 and PerC6 – have ended up becoming cell standards in labs all around the world. Possessing these cell lines, each lab has some exactly similar cells on which to test new chemical reagents, antibiotics, or drugs. Scientists can then accurately compare their results to those obtained by other labs, or perhaps to the results of past experiments. With that knowledge they can adjust the formula to make it more effective.(think vaccines)

In medicine, such common standard cell lines are necessary because the plain fact is that accurate measurement, and reproducibility of experiment results, are the cornerstones of science. Comparing results from different tissues in different labs is like comparing bananas to pineapples.

Enter cell lines HEC293 and PerC6. Use of these cell lines has already played a large role in the medical development of frequently used treatments.

But here comes the problem!

When we question where and when these helpful cell lines first originated, we find that the HEK293 cells came from the tissue of an aborted fetus in the Netherlands in 1973.

The PerC6 cell-line came from the tissues of an aborted fetus in 1985 and was developed by a proprietary company into a cell line..

So, yes, these are human fetal-tissue cell lines.

At this time it is important to note that the maintaining of the cell lines over the years has not required, or used, any further fetal tissue. They are maintained on chemical substances added to the dish. Just as my water-grown herb garden, to which I add a capful of growth chemicals every couple of weeks, produces plentiful parsley, dill, basil, and Thai basil throughout the winter.)

Now having clarified the science involved, let’s get back to the ethical question.

Should we avoid the J&J vaccine because it was developed and tested using cells derived from aborted fetal tissues?

In a perfect world the answer would obviously be yes. [ Of course, in a perfect world this concern wouldn’t have arisen in the first place.]

But God tells us (and we can easily see) that this is not a perfect world, and none of us are free from sinful actions. He has given us guidelines in His word as to how to live and make choices that are pleasing to him, but many choices are grey, not black-and-white. And none are more difficult than when two ‘good’ principles appear to point to different actions.

But before we get to those two principles, I want to muddy the waters even more.

The fact is that all three of the currently available vaccines used one of these cell lines, to a smaller or greater degree, while being produced.

Pfizer and Moderna’s use of cell lines

The Pfizer and Moderna vaccine makers used the HEK293 cell-line for two testing situations.

Prior to testing they had created the genetic mRNA strands in lab test tubes by adding chemical nucleotide ‘beads’ together. They did this until they had the coded strand needed to direct the making of the virus ‘bit’ in the vaccinated cells. This ‘bit’ is required to stimulate the body defenses. (Note – mRNA strands are not alive and did not need to be maintained in living cells)

However a necessary early part of any vaccine, or drug, production is to be sure the new vaccine doesn’t kill the cells it is treating (known as toxicity). So Moderna and Pfizer carried out tests in which the vaccine was placed within some of the HEK293 cells, to make sure the vaccine was safe for us.

Later on in the trials it was important to prove that the vaccine could stimulate the production of a good amount of antibodies (i.e. the vaccine would be effective enough to protect us). Currently the only reliable way to do that was to place the vaccine in the HEK293 cells again, and measure the amount of antibody produced in them. In this way the antibody production could be compared to the results of other labs and other vaccines, and the vaccine’s value could be proved to the FDA.

So the new mRNA vaccines of Pfizer and Moderna made use of the HEC293 cell line periodically for testing.

Johnson and Johnson’s use of cell lines

On the other hand, the J&J vaccine was made in the more traditional vaccine way. In this viral-vector(viral carrier) procedure, the vaccine is carried into the body by a disabled adenovirus. Both the vaccine and necessary parts of the adeno virus were made within cells of the PerC6 line, after the scientists had added the necessary DNA codes into them.

The continuous use of the cells is required because viruses and viral vectors are semi-alive and can’t be made in a test tube (like the mRNA vaccines), so they have to be made within some kind of cell.

So although there are differences in which cell line was used, and how the three vaccines used the cell lines, they all did use the cell lines.

Before we go on, though, I feel it is IMPORTANT TO NOTE FOR ALL THREE OF THE VACCINES:

  • there was NO freshly aborted fetal tissue involved in the testing of any of the vaccines,
  • there are NO fetal cells of any sort (old or new) within any of the vaccines..

At this point, let’s summarize what we’ve found so far:

  • Both cell lines originated from aborted fetal tissue 30-40 years ago. The deaths of the fetuses were definitely ethical problems, but ones which we (today) cannot change.
  • Neither cell line has added aborted fetal tissue since then, so that ethical problem has not been ongoing or repeated.
  • All three of the vaccines have used those cell lines, although there are differences in which cell line was used, and the amount of use that was made of it.
  • None of the vaccine producers have introduced new fetal tissues into their vaccines

Now let’s add in these facts.

  • The pandemic continues to cause pain, suffering, death, loss of livelihood, economic devastation throughout the world.
  • Using the vaccines seems to be the quickest way to control these problems
  • There is still a shortage of vaccines, which means that the J&J vaccine may be the only one offered to individuals or groups.
  • The more people who are vaccinated, the fewer people will become sick with the corona-19 virus. The fewer people who become sick, the fewer chances there are for the virus to make copies of itself, mutating while it does so. The fewer Covid 19 virus variants will be produced.
  • There are no other widespread cell lines which could have provided the needed data comparison accuracy and comparative antibody assessment quickly enough to be of use in calming this pandemic and saving lives

Finally let’s see if we can decide what to do with the Archbishop’s call to avoid the J&J vaccine

Firstly: the call to action stems from the Archbishop’s concern that aborted fetal tissue was used to originate the cell line used by J&J to make their vaccine. I can certainly understand, and agree, with his concern. A human life was killed and it appears that we are now, many years later, making use of that death for our own good. That would be sinful. and we want to obey Jesus’ first great commandment to love God with our whole heart and mind and soul and strength. I.e. we want to honor Him and the lives He creates.

The problem is, however, that if total rejection of the J&J vaccine is the right response, we should also avoid using any of the other vaccines as well, since each of the vaccines made use of cell lines originating from aborted tissue (as explained above).

Which would leave us with no acceptable vaccines.

If we follow this line of thought we still might well decide that, in order to honor God, we, individually, are prepared to risk sickness and death for ourselves, so we will choose to reject all vaccines.

But in doing so aren’t we are putting our neighbors at increased risk of infection? What about the risk to our family members who need our care and close support? To our work contacts? To the service people we buy goods from? To the world as more variants arise from more sick people?

For some of them Covid 19 infection will go badly!

Also …… will continued distancing help us love our families and neighbors in the active way that is pleasing to God? Think about it. How many of us have held back from doing our normal outreach and caring within our churches and within society because of the fear of getting infected?

All of this would seem to seriously impair our ability to obey Jesus’ second great commandment “Love your neighbor as yourself.”

So – two commandments – Love God. Love your neighbor as yourself. Both must work together in whatever situation He has put us in.


So here’s my thinking on the Archbishop’s call to avoid using the Johnson and Johnson vaccine.

We live in an imperfect world – choices and actions cannot always be perfect. There were wrong actions many years ago that we are powerless to reverse. (This is just as true for many other situations in our lives). However the original wrong action is not being repeated.

In the here and now it seems to me that loving God will best show through doing good to our neighbors in the pandemic situation in which God has placed us.

Which means getting vaccinated.

In this time of vaccine shortage, I would encourage everyone to take the first available vaccine, regardless of which one it is.

And guess what? That is not just me saying it.

In December 2020 the Vatican (one of the staunchest pro-life proponents in the world) put out a statement saying that it was morally acceptable for Roman Catholics to receive any Covid-19 vaccine, even one based on research that originally used cells derived from aborted fetuses.

Because of the severity of the situation.

And if there are no ethically alternative vaccines available!

The main points of this article are :

  • that in God’s providence the pandemic situation is still severe.
  • there are currently no ‘more ethical’, yet appropriately wide-spread, standard cell lines to use in the preparation of reliable vaccines.
  • all currently available vaccines use the cell lines in some ways – to a greater or lesser degree.
  • there is still such a shortage of vaccines that trying to pick and choose between them may cause the kind of delays that result in problems for our own, and others, health and economic situations.
  • there are currently no alternative vaccines available.
  • getting vaccinated with whatever vaccine becomes available to us may well be the most obvious way to love God and our neighbors right now.

P.S. Of course if someone pursued setting up a more ethical, world-wide (or even America-wide) cell line, I would be able to write a very different article. What about it, future scientists?