Before we begin, let's be clear - Pfizer and Janssen's Covid-19 vaccines are not still "experimental", like some people continue to claim.
Both have gone through significant clinical trials and been deemed to meet acceptable standards of safety and effectiveness by numerous global regulatory agencies including New Zealand medical regulatory body, Medsafe.
Research has found two doses of Pfizer vaccine prevents severe disease in about nine out of ten people, even against the Delta variant.
But like with all vaccines, safety and efficacy (how well they work in clinical trials) continues to be monitored.
Medsafe granted both vaccines provisional approval, essentially green-lighting them for Cabinet to make a “decision to use” as part of the Covid-19 immunisation programme. But that doesn’t mean that chapter is closed. Even once a vaccine has been rolled out, pharmaceutical companies are still required to share new clinical data and manufacturing information.
Now let’s look at the clinical trial process.
Usually, clinical trials move through three stages. Around 100 people are involved in the first trial, a few more hundred in the second, and sometimes tens of thousands in the final trial.
This process can take years - gathering the paperwork alone can take a year. At most, it could be 10 years before a new vaccine reaches the market.
But during the Covid-19 pandemic, time was a luxury no-one could afford.
In less than 12 months, Covid-19 vaccines were developed, tested, approved and rolled out, making it the fastest vaccine in history. It shattered the mumps vaccine record from the 1960s (which took around four years).
It’s important to note, speeding up doesn’t mean cutting corners.
The mRNA vaccine from Pfizer, for example, was made using technology that had been in the works since the 1990s.
If this was a normal medicine, things would move much slower. Pharmaceutical companies could take months to answer follow-up questions, not weeks, which is the time it took Pfizer to respond to Medsafe.
Pfizer also went through what's called seamless trials. Instead of moving through the levels one-by-one, some merged together. The first two trials happened simultaneously, the third, which enrolled around 44,000 people from the US, Germany, Turkey, South Africa, Brazil and Argentina, overlapped. Think of it like a concertina. This also happened with the cancer treatment called Keytruda.
Janssen did something similar. It also conducted separate trials to test single dose and double dose regimens (Medsafe has given provisional approval for a single dose).
The first follow-up data analysis was conducted and assessed by regulators (including Medsafe) in November for Pfizer, and in January for Janssen. Monitoring of participants will continue for two more years. This is common for new vaccines as it helps researchers assess the long-term safety and benefits.
It’s important to note that existing vaccines continue to be monitored in real-world use. This is called post-market monitoring and Medsafe works with the Centre for Adverse Reactions and Monitoring to collect and analyse adverse reactions reported in New Zealand. Medicines regulators may also require companies as needed to conduct specific clinical studies in people receiving the medicine or vaccine in the community.
Pfizer is also conducting additional clinical studies on different population groups such as pregnant people. These further trials are normal - it's essentially additional research for groups not included in the initial widespread trials.
Reporting disclosure statement: University of Otago professor Peter McIntyre provided expert advice for this post. It was also reviewed by The Whole Truth: Covid-19 Vaccination expert panel member Dr Collin Tukuitonga, and Medsafe.
