Which vaccine should you get?


When there are multiple shots of varying effectiveness, take whatever is available to you first

Bruce Y. Lee

While any approved vaccine has been deemed safe and effective, there is a chance some vaccines may be more effective than others.

PublishedMar 2, 2021, 5:00 am SGT


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(NYTIMES) More vaccines are coming soon.

The one-dose coronavirus vaccine developed by Johnson & Johnson was reviewed on Friday by an advisory committee for the US Food and Drug Administration (FDA), and authorised over the weekend. The FDA approved the emergency use of the vaccine, which has been shown to strongly protect recipients against severe disease and death from the coronavirus.

There are now three different shots on the market in the United States. Another available vaccine for Covid-19 will be a welcome boost to the effort of getting people vaccinated faster.

While any approved vaccine has been deemed safe and effective, there is a chance some vaccines may be more effective than others. You may wonder if you should hold out for what you perceive to be the very best vaccine, but the evidence suggests we all should get the first vaccine available to us.

The data shows the Johnson & Johnson vaccine has been 66 per cent effective at preventing moderate and severe Covid-19, and has had a 72 per cent overall efficacy rate in the US. That is a bit lower than the measured effectiveness of over 90 per cent in preventing symptomatic Covid-19 for the two-dose vaccines from Moderna and Pfizer-BioNTech.

This doesn’t mean that you should try to get one vaccine over the other. That’s for a couple of reasons: Getting as many people vaccinated as quickly as possible will save the most lives, and for any given person, a “less effective” vaccine will still provide substantial protection against severe Covid-19.

When it comes to slowing or stopping the pandemic, modelling studies from our team of public health researchers and computer scientists show that vaccinating as many people as possible sooner is more important than waiting for a vaccine with higher effectiveness.

We developed a computational simulation model of the entire US to assess what would happen if people get vaccines of varying levels of efficacy at different rates and times. As we reported in The American Journal of Preventive Medicine, in most cases, getting people vaccinated sooner with a lower efficacy vaccine prevented many more Covid-19 cases, hospitalisations and deaths compared with waiting even just a month for a higher efficacy vaccine.

Consider an example: Say the US was able to get one million people a day fully vaccinated, with a vaccine with 90 per cent efficacy (about what has been happening so far) and continued until 60 per cent of the population was fully vaccinated. At this rate, it would take about 61/2 months.

For comparison, consider a scenario where people are fully vaccinated at a faster rate of 1.5 million a day with a lower efficacy vaccine of around 70 per cent until 60 per cent of the population was fully vaccinated. At this faster rate, this would take about four months.

We found that this faster scenario with the lower efficacy vaccine could end up preventing on average over 1.38 million more cases, over 51,000 more hospitalisations, and over 6,000 more deaths than the slower vaccination, higher efficacy vaccine scenario. This underscores the importance of getting as much of the population vaccinated as soon as possible to slow the spread of the virus.

People should also avoid putting too much weight on reported vaccine effectiveness numbers in general. A vaccine’s effectiveness may vary based on your risk of catching the virus, potentially dropping as the virus becomes more widespread in a given area.

The Pfizer-BioNTech and Moderna vaccine phase 3 clinical trials started last summer, when transmission of the coronavirus was lower than it is now.

The Johnson & Johnson phase 3 trials started about two months later, on Sept 23, as the transmission of the virus was increasing, possibly because of factors like changing weather conditions and more indoor activity.

It is possible the real difference between the vaccines’ effectiveness in preventing people from getting sick from Covid-19 is smaller than reported.



Moreover, the effectiveness data that has been reported so far is only one measure of a vaccine’s benefit. There are different types of effectiveness, not just how well the vaccine prevents Covid-19 with symptoms.

For example, the Johnson & Johnson vaccine was measured to be 86 per cent effective in preventing severe Covid-19 in the US, which will cut down on crowding at hospitals. The Johnson & Johnson vaccine also requires only one dose and regular refrigeration temperatures for storage, meaning it may be easier to distribute.

Finally, this may not be the only time that you will get a Covid-19 vaccine. The vaccines may not offer lifetime protection, especially if new variants continue to emerge, and further doses may be needed to bolster immunity.

Getting any of the approved vaccines when you are eligible is important, not just for protecting yourself, but for helping get life back to normal for everyone.

• Bruce Y. Lee is the executive director of Public Health Informatics, Computational and Operations Research, a public health research group, and a professor at City University of New York Graduate School of Public Health and Health Policy.



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