Covid-19 vaccine reported to be 90% effective

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With the cautious celebration of the first effective coronavirus vaccine this week, normal life almost seems within reach. Despite remaining questions about it, scientists are generally accepting the new drug with optimism, some suggesting that life could resume some semblance of normality by spring. The announcement comes from New York City based company Pfizer, and is the first vaccine to go from development to effective in such a short amount of time. Its 90% effectiveness rate is unprecedented;  regulators have previously said that a vaccine with an effectiveness of around 50% would be approved, making the Pfizer vaccine all the more compelling.

The RNA vaccine is the first of its type to be approved for human use, and, like others in production, targets the spike proteins on the virus’ surface. The shot holds the messenger RNA which encodes this protein, and causes our own cells to synthesise it. Alone, the protein is harmless, but trains the human immune system to produce antibodies against it, without causing illness. This maintains an immunological memory that can fight the actual virus. The trials are not yet complete: so far around 43,538 participants have taken part, and 94 cases of Covid-19 have been identified. The trial will continue until 164 Covid-19 cases occur, so there is still a way to go, and questions remain.

The vaccine maintains an immunological memory against the virus

It is still unclear what level of disease the vaccine can protect against. If, in the future, severe symptoms are seen in the placebo group, it would suggest that the vaccine can prevent such cases, but none have arisen yet. It is also unknown if the vaccine is transmission blocking, where it would prevent asymptomatic patients from spreading the virus. If this was so, the end of the pandemic could be even sooner than predicted. However, this is difficult to determine, and would involve testing a larger sample size of patients. Government officials have released a priority list of those who will receive the vaccine first, with older care home residents at the top of the list, but efficacy in these and other specific demographic groups, such as over-65s, is unknown. Pfizer have stated that 42% of participants have “racially and ethnically diverse backgrounds”.

It is still unclear what level of disease the vaccine can protect against

The lasting protection of the vaccine can only be discovered over time. If the immunity doesn’t last, then it may have to be administered once a year, like the flu jab. Both the US and UK celebrated the news but urged citizens to remain cautious and continue following the lockdown restrictions. There are also logistical issues with the vaccine. Low income countries are unlikely to be able to store it without the infrastructure to maintain a -70C temperature that the vaccine needs to stabilize. This poses problems for storing it at GPs or health centres. 

Despite these unanswered questions, we will know soon if the vaccine is approved, as Pfizer is seeking an emergency use authorization from the FDA in the third week of November. The UK government has secured 40 million doses, with 10 million due before the end of the year, if no problems arise. Although some scientists are optimistic, others cast doubts on the Easter date for normalcy. Jonathan Van-Tam, the deputy chief medical officer for England, stressed the uncertainty of the situation, but said he was “Very hopeful of [a transition back to normal life] over time”.

Image: umseas via Creative Commons

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