{"id":165308,"date":"2021-01-28T20:20:46","date_gmt":"2021-01-28T17:20:46","guid":{"rendered":"https:\/\/en.buradabiliyorum.com\/covid-vaccines-how-much-protection-does-the-first-dose-provide\/"},"modified":"2021-01-28T20:20:46","modified_gmt":"2021-01-28T17:20:46","slug":"covid-vaccines-how-much-protection-does-the-first-dose-provide","status":"publish","type":"post","link":"https:\/\/buradabiliyorum.com\/en\/covid-vaccines-how-much-protection-does-the-first-dose-provide\/","title":{"rendered":"#COVID vaccines: How much protection does the first dose provide?"},"content":{"rendered":"

“#COVID vaccines: How much protection does the first dose provide?<\/strong>”<\/p>\n

\n Vaxx Populi: Israel has seen a precipitous drop in infection and hospitalization rates among those who’ve received a first dose, after 14 days\n <\/div>\n
\n Clinical trials for the two COVID-19 vaccines app<\/a>roved for use in Canada showed that they provide some protection after the first dose\u2014Pfizer\u2019s showed an efficacy of <\/span>52.4 per cent between the first and second doses<\/span><\/a>, taken 21 days apart, while <\/span>Moderna\u2019s efficacy was 80.2 per cent<\/span><\/a> between doses, taken 28 days apart. (Efficacy is the relative reduction in infection for those who are vaccinated compared to those who aren\u2019t.)<\/span><\/p>\n

Now, Israel is starting to provide real-world answers about how much protection the first dose affords. Israel has given at least one dose of the Pfizer vaccine <\/span>to roughly 40 per cent of the population<\/span><\/a>. Clalit, the country\u2019s largest health services organization, compared two groups of 200,000 members who are 60 years and older\u2014one group had been given their first dose of the vaccine and one hadn\u2019t received<\/span> it yet. For the first 12 days, the rate of those testing positive for COVID-19 was \u201crelatively constant\u201d for both groups. Then, \u201con day 14 post-vaccine, a statistically significant drop of 33 per cent in PCR positivity was witnessed in the vaccinated,\u201d explained Ran Balicer, an epidemiologist and executive at Clalit Health, <\/span>in a Twitter thread<\/span><\/a>.\u00a0<\/span><\/p>\n

RELATED:\u00a0Why is there a hold-up with Pfizer\u2019s COVID vaccines?<\/strong><\/p>\n<\/blockquote>\n

While the Clalit findings showed a<\/span> lower efficacy than the Pfizer clinical trial, <\/span>Balicer offers some explanations<\/span><\/a>: the Clalit preliminary data is raw; it doesn\u2019t account for the full 21 days between doses; and, perhaps most importantly, it only looked at those 60 and older, while the trials included adults<\/span> 16 and older.<\/span><\/p>\n

Another <\/span>Israeli health organization, Maccabi, followed 50,777 members<\/span><\/a> ages 60 years and older who got their first Pfizer doses in December and compared their infection rates to all its 480,000 senior members. The infection rates were about the same for both groups until roughly day 12, at which point infections among the general<\/a> group stayed high while those for the vaccinated group began dropping, hitting a 60 per cent drop at day 23, or two days after people had received their second dose of the vaccine.\u00a0\u00a0<\/span><\/p>\n

\u201cIt\u2019s a ray of good news<\/a>,\u201d says Jean-Paul Soucy, a Ph.D. epidemiology student at the University of Toronto and <\/span>co-creator of the authoritative COVID-19 in Canada website<\/span><\/a>, of the early information out of Israel. In particular, he notes \u201cthe quite precipitous drop\u201d by around 60 per cent in hospitalizations of new COVID-19 patients in the Maccabi data. Still, he finds the news to be \u201cslightly bittersweet,\u201d given there are many parts of Canada where long-term care residents still haven\u2019t received their first doses.\u00a0<\/span><\/p>\n

RELATED:\u00a0I\u2019m immunocompromised. Can I get the COVID-19 vaccine?<\/strong><\/p>\n<\/blockquote>\n

For all the good news, experts caution against thinking that the first dose is<\/span> any sort of guarantee against getting COVID-19. Soucy notes that no one should expect much protection during the first two weeks when there\u2019s little immune response in the body. \u201cDon\u2019t go galavanting about,\u201d he warns, cautioning that protection will be \u201cpartial at best\u201d before the second dose takes effect.\u00a0<\/span><\/p>\n

And again, there are real-world examples: In mid-January, long-term care homes in Quebec <\/span>reported COVID-19 infections<\/span><\/a> in residents who had received the first dose of either the Pfizer or Moderna vaccine. And, after the Jan. 6 insurrection at the Capitol in Washington, D.C., politicians who spent hours in crowded safe rooms together began announcing they\u2019d tested positive for COVID-19 even though they\u2019d <\/span>received their first doses<\/span><\/a> of vaccine a few days prior to the riot.\u00a0<\/span><\/p>\n

RELATED:\u00a0COVID-19 in Canada: How our battle against the second wave is going<\/strong><\/p>\n<\/blockquote>\n

And even though Israel has vaccinated a larger percentage of its population than any other country, it is still<\/span> struggling with its third wave of cases<\/span><\/a>, as the more contagious B.1.1.7 variant spreads in the population. In addition to a national lockdown, Israel stopped most international flights on Jan. 25.<\/span><\/p>\n

The really good news is that the efficacy of the two-dose Pfizer vaccine may be higher than the 95 per cent indicated in its clinical trials. On Jan. 25, the Israeli government and Maccabi released new raw data which found that out of 428,000 Israelis who had received their second doses, only 63 (or 0.014 per cent) had contracted the virus as of a week after that crucial second dose, <\/span>the <\/span>New York Times<\/span><\/i> reports<\/span><\/a>.\u00a0<\/span><\/p>\n

As Canada rolls out the country\u2019s most complex vaccination project to date,\u00a0<\/em>Maclean\u2019s\u00a0presents\u00a0<\/em>Vaxx Populi, an ongoing series<\/a> in which Patricia Treble tackles the most pressing questions related to the new COVID-19 vaccines. Send us a question you\u2019d like answered at\u00a0vaccines@macleans.ca.\u00a0If you have specific questions about your own health, we recommend consulting a family doctor or the local public health authority in your area.<\/em>
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