Attenuated live polio vaccine – to vaccinate or not to vaccinate?

In order to understand the meaning and importance (if any) of the live attenuated polio vaccine a number of things need to be done:

  1. To delve a little deeper into the subject of polio.
  2. Go back in time to the history of polio and vaccines against the virus. This is mainly to understand the differences between the two types of vaccines.
  3. Get into the topic of potential side effects, especially of the live attenuated vaccine.

Thus this chapter on the site goes down to seemingly unimportant details on initial reading, but I promise that each and every line has an importance in understanding the final conclusion that expresses my opinion.

In addition, I promise that whoever reads this chapter will enjoy the reading, will understand the importance and especially will agree with me that it is the duty of all of us to continue to vaccinate our healthy children with the attenuated live vaccine given to children in Israel at six months and a half.

What is polio?

Polio is caused by the polio virus. Infection with the virus in children is asthmatic in most cases (about 70%), and in other cases the infection can be accompanied by fever, sore throat and mild viral meningitis. However, up to 1% of those infected will later develop a mild asymmetrical paralysis in one of the limbs, a paralysis that will leave permanent damage in about two-thirds of them.

After infection of healthy people, the virus stays in the throat for up to two weeks and is excreted in the feces for up to 3-6 weeks so the person is considered contagious for that time.

I mention that you can get infected and get polio in two ways:

  • Infection of a person who is not properly vaccinated with the "wild" (or "natural" virus, meaning infection with the normal virus in nature).
  • Infection with the attenuated live virus originating from the attenuated live vaccine. Infection can occur in a person who is vaccinated with this vaccine, but also in relatives or people without proximity to the recipient of the vaccine following the transmission of the virus from person to person.

What are the types of polio virus?

There are 3 types of polio virus and they are number 1, number 2 and number 3. It is worth in my taste to briefly dwell on a number of characteristics of the various types.

The No. 1 virus is responsible for most of the "wild" polio cases in the world today.

The last case of “wild” infection with virus number 2 happened in 1999 so in 2016, the World Health Organization declared this type extinct from the world.

The latest case of “wild” infection with virus number 3 was reported in 2012, and recently (October 2019) the World Health Organization also announced the extinction of this type.

In this context it is interesting to add that human is the sole host of the virus in nature. In practice this means that I hope that a day will come when most of the children of the world will be vaccinated against this virus and later there will be days when the polio virus will disappear from the world. And maybe one day this episode will become unnecessary as well as the vaccines against this virus.

What are the vaccines against polio?

There are two vaccines against polio and they are the killed vaccine and the live attenuated vaccine.

The killed vaccine was developed by Yona Salk – contains the three types of killed polio virus. The vaccine is given by injection into a muscle, usually in combination with other childhood vaccines.

The attenuated live vaccine developed by Albert Sabin – The original vaccine contained the three types in the form of attenuated live viruses. However, following the World Health Organization’s announcement in April 2016 of the extinction of type 2 of the virus, the attenuated live vaccine against the three types was removed (it was called the trivalent vaccine) and a new vaccine against the first and third types only was introduced worldwide (bivalent vaccine).

I anticipate that with the announcement of the eradication of type 3 as well (October 2019), the live attenuated vaccine will soon change and include only the first type of virus.

What do the killed vaccine and the live attenuated vaccine have in common?

The two vaccines are similar in that they are very effective in preventing polio in those who receive the vaccine series properly. In the laboratory, after 2 doses of killed vaccine, about 99% of the vaccinees develop a good amount of antibodies against the three types of virus (100% after 3 doses). Also practically, the two vaccines provide excellent protection and those vaccinated will not get paralyzing from the "wild" virus.

What is the main difference between the killed vaccine and the attenuated live vaccine?

Beyond the different route of administration ( inactivated by injection into a muscle, live attenuated by drops in the mouth) there is a fundamental difference between the two vaccines that is important to understand.

A person vaccinated with the killed vaccine may be protected from paralysis but may still be a carrier of the virus in the gut and thus may be part of the carrying reservoir. The implication is that this person, even though vaccinated with the killed vaccine and will not get sick, can still pass on the virus in the feces in a way that may infect other people.

In contrast, a person vaccinated with the attenuated live vaccine is also protected from disease, but in addition will develop antibodies in the digestive tract against the virus. These antibodies do not allow that person to be infected with the virus at all and carry it in the digestive tract. Thus, those who are properly vaccinated with the attenuated live vaccine will not be part of the carrier and infection chain because they cannot excrete the virus in the feces.

Pay attention to the wording as it appears in the vaccination guide of the State of Israel:

The killed vaccine "gives the individual the optimal protection." They say, whoever gets vaccinated with the killed vaccine will not get polio.

The attenuated live vaccine "given for optimal intestinal immunity and to reduce the transmission of the virus in the community."

Why is this important and practical for all of us? Going forward.

I will add for the sake of meticulousness among us that it is preferable to give the drops (live attenuated vaccine) at least two hours before or after feeding in breast milk (breastfeeding or pumped bottle), in order to avoid contact of the vaccine with antibodies in breast milk. However, according to the Ministry of Health’s instructions, the vaccination should not be delayed due to this, and a dose given not within this period of time is also considered a proper dose.

Who can not get a polio vaccine?

Children (you could write people instead of children, but the site focuses on children of course) who are known to be sensitive to one of the vaccine components or who have experienced a severe allergic reaction after a previous vaccination cannot receive a killed or attenuated live vaccine.

Immunosuppressed children (congenital or acquired primary immunosuppression, oncology patients, patients receiving immunosuppressive drugs, etc.) cannot receive live attenuated polio vaccine for fear of contracting the virus from the vaccine as detailed below.

Even healthy children who have a first-degree relative who is vaccinated are unable to get the live vaccine attenuated because the virus from the vaccine may be excreted in the feces and may infect the vaccinated family member. If there is a child who has a first-degree relative who is vaccinated, then the contact between the two should be reduced to a period of 6 weeks. In addition, in this case the personal hygiene of the person suppressed by the vaccine must be observed including the washing of hands with soap and water, especially after using the toilet or before contact with food.

Children who have a first-degree relative who is pregnant can be given the live attenuated vaccine without fear.

What are the common side effects of both types of polio vaccines?

The killed vaccine – sensitivity at the injection site and sometimes restlessness and fever in the 24 hours after the vaccine. An allergic reaction resulting from sensitivity to one of the components of the vaccine is rare.

The attenuated live vaccine – an allergic reaction resulting from sensitivity to one of the components of the vaccine is rare.

What is the rare side effect of contracting a virus after a live attenuated vaccine?

Recall that since this is a live attenuated vaccine then as we wrote, this vaccine should not vaccinate immunocompromised patients (or first-degree relatives of immunocompromised people) for fear of contracting the virus.

But infection (in a vaccinated person, relatives or people who are not in close proximity to a vaccinated person) can also occur when a healthy child is vaccinated with this vaccine. The prevalence of this infection is 1 in 2.4 million attenuated live vaccine doses given. This prevalence is higher after the first dose of live attenuated vaccine and is calculated as 1 in 750,000 doses. The vaccination briefing of the State of Israel quoted an incidence of less than 1 per million vaccine doses in the person receiving the vaccine or in his immediate environment.

In fact, thanks to the two vaccines (killed and attenuated live), many countries in the world have reached a point where the "wild" polio cases have been zeroed. But on the other hand, the rare side effect of infection after attenuated live vaccine has led to a situation where countries that migrated the "wild" polio but continued to vaccinate with attenuated live vaccine ended up with more cases (rare as they may be) of vaccine-related polio than "wild" polio. For example, the last polio case that has been acquired in the United States (as opposed to "imported" cases) that occurred as a result of the "wild" virus occurred in 1979. Subsequent to the year 2000, when the attenuated live vaccine was discontinued in the United States, approximately 6-8 cases per year of attenuated live vaccine-related cases were diagnosed in the United States.

What has happened in the State of Israel or how and why has the vaccination routine changed in recent years?

In fact, from 2005 to 2013, in the State of Israel, like many Western countries, only a killed vaccine was used.

But, in 2013 the virus was discovered in wastewater samples almost all over the country as part of routine national monitoring carried out for this virus.

It is interesting to ask how it happened that Israel was the only country where the virus was in the sewage. This is probably related to monitoring that is carried out in Israel but is not carried out in other countries, not even in developed Western countries.

The significance of finding the virus in the wastewater was enormous:

The discovery of the virus indicated that there were people in the State of Israel who had the virus in their intestines.

This means that theoretically it is only a matter of time before the virus infects a person who is not properly vaccinated and he develops paralysis, and here Israel will become one of the few countries in the world where there is clinical polio (we could join a dubious list of polio countries like Afghanistan, Nigeria and Pakistan).

Therefore, and following what I wrote earlier about the differences between the two types of vaccines, the State of Israel launched an operation to supplement a live attenuated vaccine for children and in addition it was decided to return the use of attenuated live vaccine routines. The thinking was that giving the addition of the attenuated live vaccine, as I wrote earlier, would eliminate the possibility that the virus could even pass through the intestines of children vaccinated with the attenuated live vaccine and the transmission of the virus would stop.

Again, as I also wrote in other chapters action speaks louder than words I vaccinated my three children with the attenuated live vaccine in the same vaccination campaign in 2013 (on 04/09/2013).

Therefore, starting in 2013 and currently, Israeli children receive vaccines against polio at the following ages:

Inactivated vaccine is given at monthly ages, 4 months, 6 months and one year – given by injection into a muscle within the pentagonal vaccine which also includes diphtheria, tetanus, pertussis and B-type influenza influenzae

Inactivated vaccine is given in the second grade – it is given by injection into a muscle in a square vaccine that also includes diphtheria, tetanus and pertussis.

A live attenuated vaccine is given orally at the age of six months and a year and a half. According to the vaccination guide, attenuated live vaccine can only be given to children up to the age of two.

And now the first big question (out of two) - how can I join the recommendation to give a live attenuated vaccine that rarely causes disease while clinical polio cases have not been in the State of Israel?

Well, because there are 2 reasons why any child who is vaccinated with the attenuated live vaccine in Israel will not get polio and they are:

A. A polio related to the live vaccine has never been described in a person who has been previously vaccinated with the killed vaccine. Want to say that the fact that the child receives the attenuated live vaccine at the age of six months after having received two doses of Inactivated vaccine (and another one at the age of six months, with the first dose of attenuated live vaccine and the fact he already has antibodies against the virus, eliminating the possibility that the child will become ill with polio because attenuated live vaccine . For example, in Israel in the years 1990-2004, when the routine of vaccinations was a combination of both types of vaccines, there was not a single case of disease associated with the attenuated live vaccine. Care should be taken in this context to ensure that the live attenuated vaccine is given only to children who have already received 2 doses of inactivated vaccine or to children who have received only one dose of the inactivated vaccine and receive the live attenuated vaccine (first dose) along with the second dose of the inactivated vaccine.

B. In the past, most cases of disease that occurred after attenuated live vaccines were caused by a type 2 polio virus. The fact that the live attenuated vaccine given in Israel (and around the world, of course) is a bivalent vaccine that does not contain this type, further reduces the chance of a vaccine-related illness.

And now the second question - why even vaccinate with attenuated live vaccine if I wrote that whoever gets Inactivated vaccine will never get sick?

(After all, what do we care that the virus will be in the sewage if all the children of the State of Israel are vaccinated with the killed vaccine and I promised that they would not get sick?)

If I could guarantee that all children of the State of Israel would receive an Inactivated vaccine and inevitably produce antibodies against the virus then I would say that there is no need for an attenuated live vaccine (in a very narrow view for the good of the children of Israel, it is clear to me that there are other interests) .

But unfortunately not all children of the State of Israel can be vaccinated and develop antibodies properly to this virus. These are of course children (again, I could write people instead of the word children) who even when vaccinated with the inactivated vaccine will not respond with proper antibody production due to being immunosuppressed due to congenital or acquired medical condition (oncological children or children receiving immunosuppressive drugs).

Therefore, in my opinion, we should all continue to vaccinate our children even with the attenuated live vaccine in order to reduce as much as possible the presence of the virus in our area. In this way we also protect those children whose fate has improved less in the context of their immune system.

I recently heard another argument from parents of healthy children who have not been vaccinated with the attenuated live vaccine is that they do not want to protect the families of vaccine opponents who do not vaccinate healthy children by choice and enjoy herd immunity and the fact that the virus is not found because others are vaccinated. This in my opinion is not at all relevant to the current discussion and I am really not there.

I want to focus on children with the least good immune system who cannot develop antibodies and be protected against this virus. We all have a family member or acquaintances like that, and in my opinion, as a society we have a role and that is to protect the "weak".

At the end of the day we are all brothers and sisters and there is no knowing when we or our relatives will be part of those who need the protection and the help from society.

I urge all parents to act like me, say thank you every day, and continue to vaccinate our healthy children even with the attenuated live polio vaccine.