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Limitations of COVID-19 Vaccination

There are some good reasons to be optimistic about the ongoing coronavirus pandemic. Both Pfizer and Moderna have reported that their vaccines are more than 90% effective; optimistic (though admittedly less reliable) reports are also coming out of China and Russia. Between these early successes and the sheer number of other vaccine candidates in development, it seems increasingly likely that there will be a safe and effective vaccine in the near future. Unfortunately, this does not mean that the pandemic will be over any time soon.

First, drug development is a difficult and unpredictable process; historically, only about 6% of vaccines have moved from the preclinical phase to market. Thankfully, this number does not apply to these coronavirus vaccines – aside from the positive preliminary results, all these candidates have already reached the third and final phase of clinical trials. Many of the vaccine candidates also rely on new vaccine technologies, so the same historical rates of success may not apply.

But this in itself could be cause for concern. Clinical trials normally take many years, for good reason. The accelerated process that is being used for these vaccine candidates, and the pressure for success, might result in the approval of a vaccine that is ineffective in the long-term, or that has dangerous side effects.

Assuming that the vaccines are approved and are truly effective and safe, it would still take quite some time for the pandemic to fully come to an end. In order to achieve herd immunity, up to 75% of the global population will need to be immune; with a vaccine efficacy of 90%, that means that 78.5% of the population will need to be inoculated, or about 6 billion people.

Since many of the vaccine candidates require two applications, this means that up to 12 billion doses will need to be manufactured and shipped. This is an enormous undertaking, one that is even more daunting when considering that vaccines carry special storage requirements (the Pfizer vaccine in particular will need to be shipped in specially designed containers filled with dry ice). There are many other difficulties to overcome, some of them deceptively simple, like obtaining enough medical vials for storage.

Distribution has its own complications. First, since supplies will initially be limited, it remains to be seen how they will be divided between countries. One possible mechanism is cooperation through COVAX, an initiative to provide financing to a large number of vaccine options and to equitably distribute successful vaccines between participating states. Through this framework, wealthier countries would subsidize vaccine costs for middle- and lower-income countries, and in return receive some benefits, like a certain amount of choice in which vaccines they receive.

Ideally, this approach has several benefits, even if there are some concerns about its implementation. In diversifying funding for vaccines, it stimulates the development of multiple options and keeps countries from losing out if the specific set of vaccines that they choose to pre-order are not ultimately viable.

In addition, such an approach ensures that lower-income countries will not significantly trail behind wealthier nations in vaccinating their populations. The benefits of this go beyond equity; while widespread vaccination in a wealthy country will make things much easier within its borders, life there will only fully stabilize once immunization has been achieved on a global scale.

As it stands, COVAX is lacking in support, most notably from the United States (although there are indications that Joe Biden will reverse this position). Even wealthy governments that support the program have also unilaterally preordered vaccines, which largely defeats the purpose. In anticipating that some vaccines will not be effective, some countries, most notably Canada, have ordered far more vaccines than they could possibly need. This could lead to inefficient distribution that further limits vaccine availability in poorer countries, as exemplified by this unfortunate article.

Within countries, governments will need to decide who to prioritize and find ways to get the vaccines to those who most need them. The United Arab Emirates has already begun provisional immunization of medical workers taking care of COVID-19 patients, using Chinese vaccines that are currently still under clinical review; other countries will also likely prioritize healthcare workers once vaccines have been fully cleared. Older people and those with preexisting conditions are also first in line, though there are arguments that this population will be better served by prioritizing children instead.

It might be possible to cut down on the number of vaccines needed by vaccinating only those who have not already been infected with COVID-19. However, it is not clear if the immunity provided by prior infection is equivalent to immunity from vaccines, and so guidelines have not yet been established. If those who have been infected previously can be safely excluded, this will free up quite a few doses, especially in certain areas – there are estimates that as many as 1 in 3 people in New York state already have antibodies. However, coming up with a system to track all those who already have immunity would add another level of complication to an already difficult process; plenty of people are unaware of their status and would need to be tested for antibodies, especially when considering recent evidence that the virus had been circulating – outside of China – months before it had first been identified.

Even if all of these logistical challenges are overcome, vaccine hesitancy could pose a challenge. A recent study in the United States found enough resistance to coronavirus vaccination among the population that it alone could prevent achieving herd immunity outright. This skepticism is not necessarily limited to those who avoid vaccines in general – indeed, the main reason for wanting to avoid the vaccine was due to concern that potential side effects might not be fully understood due to its novelty. Given how quickly clinical trials are being performed, this concern is understandable; convincing the public that the vaccines are safe will be a significant challenge for governments and industry.

Despite all of these challenges, the most recent announcements are great news. Even so, there are still many unknowns going forward, meaning that widespread inoculation could very well still be more than a year away. Companies and individuals should plan to continue to take pandemic-related precautions, as we’ve discussed in previous posts, for the foreseeable future.

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