• home
• about pkids
• diseases
• families
• infection protection
• immunizations
• media room
• Your Choice!
• getvaxed
• cme

Immunizations

How Are Vaccines Made and Why Do They Work?  In their book Vaccines: What Every Parent Should Know, Dr. Paul Offit and Dr. Louis Bell take the complex question of how vaccines are made and answer it in a way we can all understand: Vaccines are made by taking viruses or bacteria and weakening them so that they can’t reproduce (or replicate) themselves very well or so that they can’t replicate at all. Children given vaccines are exposed to enough of the virus or bacteria to develop immunity, but not enough to make them sick. There are four ways that viruses and bacteria are weakened to make vaccines: Change the virus blueprint (or genes) so that the virus replicates poorly. This is how the measles, mumps, rubella, and varicella vaccines are made. The virus blueprint is changed  by a technique called cell culture adaptation [adapting a virus   to grow in specialized cells grown in the lab instead of the cells it normally grows in]. Because viruses can still, to some extent, make copies of themselves after cell culture adaptation (and therefore are still alive), they are often referred to as live, attenuated (or weakened) viruses. Destroy the virus blueprint (or genes) so that the virus can’t replicate at all. This is how the “killed” polio vaccine (or polio shot) is made. Vaccine virus is made by treating polio virus  with the chemical formaldehyde. This treatment permanently destroys the polio genes so  that the virus can no longer replicate. Use only a part of the virus or bacteria. This is how the Hib, hepatitis B, and (in part) pertussis vaccines are made.    Because the viral or bacterial genes are not present in the vaccine, the viruses or bacteria can’t replicate. Take the toxin that is released from the bacteria, purify it, and kill it so it can’t do any harm. Some bacteria cause disease  not by replicating but by manufacturing harmful proteins  called toxins. For example, bacteria like diphtheria, tetanus, and pertussis (whooping cough) all cause disease by producing toxins. To make vaccines against these bacteria, toxins are purified and killed with chemicals (such as formaldehyde). Again, because bacterial genes are not part of the vaccine, bacteria can’t replicate. Vaccine Boosters Because the immune response from some vaccines may decrease over time, vaccines known as “boosters” are sometimes given  to restore the immune response against that particular germ. Protective immunity lasts longer when boosters are given. Tetanus boosters, for example, are recommended every 10 years starting at age 10 or 11. A study published in May 2002 by the Annals of Internal Medicine revealed that millions of Americans are vulnerable to tetanus and diphtheria infections because their booster shots have not been kept up to date. On other fronts in the vaccine field, scientists are trying to find new ways of producing vaccines, particularly using biotechnology and genetic engineering. These new methods would make it unnecessary to produce large quantities of the dangerous pathogens to make vaccines. Passive Immunity In addition to natural or “vaccine-induced” immunity to diseases, there is also “passive” immunity. Passive immunity occurs when someone is injected directly with large quantities of antibodies that are ready to immediately fight a specific virus or bacteria. These antibodies go to work immediately against any antigen or pathogen. There is no waiting period, as is needed by some vaccines, before sufficient antibodies are produced. However, protection from these antibody injections is temporary. Once the antibodies are cleared from the body, no new antibodies are made. Doctors use this approach to treat people who have been exposed to hepatitis B, hepatitis A and rabies. Babies born to mothers with hepatitis B are immediately treated with hepatitis B antibodies (called HBIG or hepatitis B immune globulin) and  simultaneously immunized against hepatitis B   to prevent any infection that might have occurred during the birth process. Next Page: Monitoring Vaccines for Safety Previous Page: The Immune System vs. Germs   Important disclaimer: The information on pkids.org is for educational purposes only and should not be considered to be medical advice. It is not meant to replace the advice of the physician who cares for your child. All medical advice and information should be considered to be incomplete without a physical exam, which is not possible without a visit to your doctor.

The patient who died of Covid-19 may have received a placebo.

It is sad for the doctor who died but his sacrifice opens the door for a safe vaccine. 

Covid: No safety concerns found with Oxford vaccine trial after Brazil death

Published

4 days ago

Related Topics

• Coronavirus pandemic

IMAGE COPYRIGHTREUTERS

image captionBrazil has been conducting trials of the vaccine

Trials of a Covid-19 vaccine being developed by AstraZeneca and Oxford University will continue, following a review into the death of a volunteer in Brazil.

Brazil's health authority has given no details about the death, citing confidentiality protocols.

Oxford University said a "careful assessment" had revealed no safety concerns.

The BBC understands that the volunteer did not receive the vaccine.

Only around half the volunteers in the trial are given the actual Oxford University Covid-19 vaccine. The second group are being given an existing licensed vaccine for meningitis. 

Neither the participants nor their families know which vaccine they are being given. 

This enables the researchers to compare the results for the two groups in order to measure whether the vaccine is effective.

• How close are we to a coronavirus vaccine?
• Oxford University to resume Covid-19 vaccine trial
• Oxford coronavirus vaccine triggers immune response

AstraZeneca said in a statement that it could not comment on individual cases but it "can confirm that all required review processes have been followed". 

"All significant medical events are carefully assessed by trial investigators, an independent safety monitoring committee and the regulatory authorities," it said. "These assessments have not led to any concerns about continuation of the ongoing study."

There are high hopes that the Oxford/AstraZeneca vaccine could be one of the first to make it onto the market.

It had successful phase 1 and 2 testing, while phase 3 testing is being carried out on participants in countries including the UK, Brazil and India.

Trials of the Oxford vaccine were paused last month after a reported side effect in a patient in the UK, but were resumed days later when it was deemed safe to continue.

Phase 3 trials in the US remain on hold while the regulator there conducts its own assessment. A senior official was quoted by Bloomberg on Wednesday as saying he expected US trials to restart later in the week.

Trial 'should continue'

Brazil's health authority Anvisa said it was informed of the Brazilian volunteer's death on 19 October. 

Brazilian media report that the volunteer was a 28-year-old doctor who died of Covid-19 complications. They say the doctor had worked with infected patients. 

This has not been publicly confirmed by Anvisa.

In a statement, Oxford University said: "All significant medical incidents, whether participants are in the control group or the Covid-19 vaccine group, are independently reviewed.

"The independent review, in addition to the Brazilian regulator, have both recommended that the trial should continue," it said.

Brazil has plans to purchase the vaccine if it is approved.

The country has had nearly 5.3 million confirmed coronavirus cases - the third highest tally in the world after the US and India - and is second only to the US in terms of deaths, with nearly 155,000 registered so far, according to data collated by Johns Hopkins University.